scholarly journals The Two-Component Monooxygenase MeaXY Initiates the Downstream Pathway of Chloroacetanilide Herbicide Catabolism in Sphingomonads

2017 ◽  
Vol 83 (7) ◽  
Author(s):  
Minggen Cheng ◽  
Qiang Meng ◽  
Youjian Yang ◽  
Cuiwei Chu ◽  
Qing Chen ◽  
...  
Keyword(s):  
Ring Cleavage ◽  
Monooxygenase System ◽  
Biochemical Pathway ◽  
Catabolic Pathway ◽  
Aniline Derivative ◽  
Content Type ◽  
The Past ◽  
Chloroacetanilide Herbicides ◽  
Two Component ◽  
Key Genes

ABSTRACT Due to the extensive use of chloroacetanilide herbicides over the past 60 years, bacteria have evolved catabolic pathways to mineralize these compounds. In the upstream catabolic pathway, chloroacetanilide herbicides are transformed into the two common metabolites 2-methyl-6-ethylaniline (MEA) and 2,6-diethylaniline (DEA) through N-dealkylation and amide hydrolysis. The pathway downstream of MEA is initiated by the hydroxylation of aromatic rings, followed by its conversion to a substrate for ring cleavage after several steps. Most of the key genes in the pathway have been identified. However, the genes involved in the initial hydroxylation step of MEA are still unknown. As a special aniline derivative, MEA cannot be transformed by the aniline dioxygenases that have been characterized. Sphingobium baderi DE-13 can completely degrade MEA and use it as a sole carbon source for growth. In this work, an MEA degradation-deficient mutant of S. baderi DE-13 was isolated. MEA catabolism genes were predicted through comparative genomic analysis. The results of genetic complementation and heterologous expression demonstrated that the products of meaX and meaY are responsible for the initial step of MEA degradation in S. baderi DE-13. MeaXY is a two-component flavoprotein monooxygenase system that catalyzes the hydroxylation of MEA and DEA using NADH and flavin mononucleotide (FMN) as cofactors. Nuclear magnetic resonance (NMR) analysis confirmed that MeaXY hydroxylates MEA and DEA at the para-position. Transcription of meaX was enhanced remarkably upon induction of MEA or DEA in S. baderi DE-13. Additionally, meaX and meaY were highly conserved among other MEA-degrading sphingomonads. This study fills a gap in our knowledge of the biochemical pathway that carries out mineralization of chloroacetanilide herbicides in sphingomonads. IMPORTANCE Much attention has been paid to the environmental fate of chloroacetanilide herbicides used for the past 60 years. Microbial degradation is considered an important mechanism in the degradation of these compounds. Bacterial degradation of chloroacetanilide herbicides has been investigated in many recent studies. Pure cultures or consortia able to mineralize these herbicides have been obtained. The catabolic pathway has been proposed, and most key genes involved have been identified. However, the genes responsible for the initiation step (from MEA to hydroxylated MEA or from DEA to hydroxylated DEA) of the downstream pathway have not been reported. The present study demonstrates that a two-component flavin-dependent monooxygenase system, MeaXY, catalyzes the para-hydroxylation of MEA or DEA in sphingomonads. Therefore, this work finds a missing link in the biochemical pathway that carries out the mineralization of chloroacetanilide herbicides in sphingomonads. Additionally, the results expand our understanding of the degradation of a special kind of aniline derivative.

scholarly journals A Novel Aerobic Degradation Pathway for Thiobencarb Is Initiated by the TmoAB Two-Component Flavin Mononucleotide-Dependent Monooxygenase System in Acidovorax sp. Strain T1

2017 ◽  
Vol 83 (23) ◽  
Author(s):  
Cui-Wei Chu ◽  
Bin Liu ◽  
Na Li ◽  
Shi-Gang Yao ◽  
Dan Cheng ◽  
...  
Keyword(s):  
Microbial Degradation ◽  
Bond Cleavage ◽  
Degradation Pathway ◽  
Transcriptional Analysis ◽  
Flavin Mononucleotide ◽  
Monooxygenase System ◽  
Chlorobenzoic Acid ◽  
Content Type ◽  
Catabolic Genes ◽  
Two Component

ABSTRACT Thiobencarb is a thiocarbamate herbicide used in rice paddies worldwide. Microbial degradation plays a crucial role in the dissipation of thiobencarb in the environment. However, the physiological and genetic mechanisms underlying thiobencarb degradation remain unknown. In this study, a novel thiobencarb degradation pathway was proposed in Acidovorax sp. strain T1. Thiobencarb was oxidized and cleaved at the C—S bond, generating diethylcarbamothioic S-acid and 4-chlorobenzaldehyde (4CDA). 4CDA was then oxidized to 4-chlorobenzoic acid (4CBA) and hydrolytically dechlorinated to 4-hydroxybenzoic acid (4HBA). The identification of catabolic genes suggested further hydroxylation to protocatechuic acid (PCA) and finally degradation through the protocatechuate 4,5-dioxygenase pathway. A novel two-component monooxygenase system identified in the strain, TmoAB, was responsible for the initial catabolic reaction. TmoA shared 28 to 32% identity with the oxygenase components of pyrimidine monooxygenase from Agrobacterium fabrum, alkanesulfonate monooxygenase from Pseudomonas savastanoi, and dibenzothiophene monooxygenase from Rhodococcus sp. TmoB shared 25 to 37% identity with reported flavin reductases and oxidized NADH but not NADPH. TmoAB is a flavin mononucleotide (FMN)-dependent monooxygenase and catalyzed the C—S bond cleavage of thiobencarb. Introduction of tmoAB into cells of the thiobencarb degradation-deficient mutant T1m restored its ability to degrade and utilize thiobencarb. A dehydrogenase gene, tmoC, was located 7,129 bp downstream of tmoAB, and its transcription was clearly induced by thiobencarb. The purified TmoC catalyzed the dehydrogenation of 4CDA to 4CBA using NAD+ as a cofactor. A gene cluster responsible for the complete 4CBA metabolic pathway was also cloned, and its involvement in thiobencarb degradation was preliminarily verified by transcriptional analysis. IMPORTANCE Microbial degradation is the main factor in thiobencarb dissipation in soil. In previous studies, thiobencarb was degraded initially via N-deethylation, sulfoxidation, hydroxylation, and dechlorination. However, enzymes and genes involved in the microbial degradation of thiobencarb have not been studied. This study revealed a new thiobencarb degradation pathway in Acidovorax sp. strain T1 and identified a novel two-component FMN-dependent monooxygenase system, TmoAB. Under TmoAB-mediated catalysis, thiobencarb was cleaved at the C—S bond, producing diethylcarbamothioic S-acid and 4CDA. Furthermore, the downstream degradation pathway of thiobencarb was proposed. Our study provides the physiological, biochemical, and genetic foundation of thiobencarb degradation in this microorganism.

scholarly journals Identification and Characterization of a Tetramethylpyrazine Catabolic Pathway in Rhodococcus jostii TMP1

2013 ◽  
Vol 79 (12) ◽  
pp. 3649-3657 ◽  
Author(s):  
Simonas Kutanovas ◽  
Jonita Stankeviciute ◽  
Gintaras Urbelis ◽  
Daiva Tauraite ◽  
Rasa Rutkiene ◽  
...  
Keyword(s):  
Expression Profiles ◽  
Bacterial Degradation ◽  
Ring Cleavage ◽  
Published Data ◽  
Catabolic Pathway ◽  
Genome Database ◽  
Content Type ◽  
Intermediate Metabolites ◽  
Inducible Protein ◽  
Rhodococcus Jostii

ABSTRACTAt present, there are no published data on catabolic pathways ofN-heterocyclic compounds, in which all carbon atoms carry a substituent. We identified the genetic locus and characterized key reactions in the aerobic degradation of tetramethylpyrazine inRhodococcus jostiistrain TMP1. By comparing protein expression profiles, we identified a tetramethylpyrazine-inducible protein of 40 kDa and determined its identity by tandem mass spectrometry (MS-MS)de novosequencing. Searches against anR. jostiiTMP1 genome database allowed the identification of the tetramethylpyrazine-inducible protein-coding gene. The tetramethylpyrazine-inducible gene was located within a 13-kb genome cluster, denominated the tetramethylpyrazine degradation (tpd) locus, that encoded eight proteins involved in tetramethylpyrazine catabolism. The genes from this cluster were cloned and transferred into tetramethylpyrazine-nondegradingRhodococcus erythropolisstrain SQ1. This allowed us to verify the function of thetpdlocus, to isolate intermediate metabolites, and to reconstruct the catabolic pathway of tetramethylpyrazine. We report that the degradation of tetramethylpyrazine is a multistep process that includes initial oxidative aromatic-ring cleavage by tetramethylpyrazine oxygenase, TpdAB; subsequent hydrolysis by (Z)-N,N′-(but-2-ene-2,3-diyl)diacetamide hydrolase, TpdC; and further intermediate metabolite reduction by aminoalcohol dehydrogenase, TpdE. Thus, the genes responsible for bacterial degradation of pyrazines have been identified, and intermediate metabolites of tetramethylpyrazine degradation have been isolated for the first time.

scholarly journals 3,6-Dichlorosalicylate Catabolism Is Initiated by the DsmABC Cytochrome P450 Monooxygenase System inRhizorhabdus dicambivoransNdbn-20

2017 ◽  
Vol 84 (4) ◽  
Author(s):  
Na Li ◽  
Li Yao ◽  
Qin He ◽  
Jiguo Qiu ◽  
Dan Cheng ◽  
...  
Keyword(s):  
Cytochrome P450 ◽  
Bioinformatic Analysis ◽  
Heme Iron ◽  
Cytochrome P450 Monooxygenase ◽  
Monooxygenase System ◽  
Catabolic Pathway ◽  
P450 Monooxygenase ◽  
Content Type ◽  
Promising Target

ABSTRACTThe degradation of the herbicide dicamba is initiated by demethylation to form 3,6-dichlorosalicylate (3,6-DCSA) inRhizorhabdusdicambivoransNdbn-20. In the present study, a 3,6-DCSA degradation-deficient mutant, Ndbn-20m, was screened. A cluster,dsmR1DABCEFGR2, was lost in this mutant. The cluster consisted of nine genes, all of which were apparently induced by 3,6-DCSA. DsmA shared 30 to 36% identity with the monooxygenase components of reported three-component cytochrome P450 systems and formed a monophyletic branch in the phylogenetic tree. DsmB and DsmC were most closely related to the reported [2Fe-2S] ferredoxin and ferredoxin reductase, respectively. The disruption ofdsmAin strain Ndbn-20 resulted in inactive 3,6-DCSA degradation. WhendsmABC, but notdsmAalone, was introduced into mutant Ndbn-20m andSphingobium quisquiliarumDC-2 (which is unable to degrade salicylate and its derivatives), they acquired the ability to hydroxylate 3,6-DCSA. Single-crystal X-ray diffraction demonstrated that the DsmABC-catalyzed hydroxylation occurred at the C-5 position of 3,6-DCSA, generating 3,6-dichlorogentisate (3,6-DCGA). In addition, DsmD shared 51% identity with GtdA (a gentisate and 3,6-DCGA 1,2-dioxygenase) fromSphingomonassp. strain RW5. However, unlike GtdA, the purified DsmD catalyzed the cleavage of gentisate and 3-chlorogentisate but not 6-chlorogentisate or 3,6-DCGAin vitro. Based on the bioinformatic analysis and gene function studies, a possible catabolic pathway of dicamba inR. dicambivoransNdbn-20 was proposed.IMPORTANCEDicamba is widely used to control a variety of broadleaf weeds and is a promising target herbicide for the engineering of herbicide-resistant crops. The catabolism of dicamba has thus received increasing attention. Bacteria mineralize dicamba initially via demethylation, generating 3,6-dichlorosalicylate. However, the catabolism of 3,6-dichlorosalicylate remains unknown. In this study, we cloned a gene cluster,dsmR1DABCEFGR2, involved in 3,6-dichlorosalicylate degradation fromR. dicambivoransNdbn-20, demonstrated that the cytochrome P450 monooxygenase system DsmABC was responsible for the 5-hydroxylation of 3,6-dichlorosalicylate, and proposed a dicamba catabolic pathway. This study provides a basis to elucidate the catabolism of dicamba and has benefits for the ecotoxicological study of dicamba. Furthermore, the hydroxylation of salicylate has been previously reported to be catalyzed by single-component flavoprotein or three-component Rieske non-heme iron oxygenase, whereas DsmABC was the only cytochrome P450 monooxygenase system hydroxylating salicylate and its methyl- or chloro-substituted derivatives.

scholarly journals Metabolic Pathway Involved in 2-Methyl-6-Ethylaniline Degradation by Sphingobium sp. Strain MEA3-1 and Cloning of the Novel Flavin-Dependent Monooxygenase SystemmeaBA

2015 ◽  
Vol 81 (24) ◽  
pp. 8254-8264 ◽  
Author(s):  
Weiliang Dong ◽  
Qiongzhen Chen ◽  
Ying Hou ◽  
Shuhuan Li ◽  
Kai Zhuang ◽  
...  
Keyword(s):  
Metabolic Pathway ◽  
Monooxygenase System ◽  
The Novel ◽  
P450 Monooxygenase ◽  
Content Type ◽  
Protein Mass ◽  
Sequence Identity ◽  
Chloroacetanilide Herbicides ◽  
Intermediate Metabolites ◽  
Dimensional Electrophoresis

ABSTRACT2-Methyl-6-ethylaniline (MEA) is the main microbial degradation intermediate of the chloroacetanilide herbicides acetochlor and metolachlor.Sphingobiumsp. strain MEA3-1 can utilize MEA and various alkyl-substituted aniline and phenol compounds as sole carbon and energy sources for growth. We isolated the mutant strain MEA3-1Mut, which converts MEA only to 2-methyl-6-ethyl-hydroquinone (MEHQ) and 2-methyl-6-ethyl-benzoquinone (MEBQ). MEA may be oxidized by the P450 monooxygenase system to 4-hydroxy-2-methyl-6-ethylaniline (4-OH-MEA), which can be hydrolytically spontaneously deaminated to MEBQ or MEHQ. The MEA microbial metabolic pathway was reconstituted based on the substrate spectra and identification of the intermediate metabolites in both the wild-type and mutant strains. Plasmidome sequencing indicated that both strains harbored 7 plasmids with sizes ranging from 6,108 bp to 287,745 bp. Among the 7 plasmids, 6 were identical, and pMEA02′ in strain MEA3-1Mut lost a 37,000-bp fragment compared to pMEA02 in strain MEA3-1. Two-dimensional electrophoresis (2-DE) and protein mass fingerprinting (PMF) showed that MEA3-1Mut lost the two-component flavin-dependent monooxygenase (TC-FDM) MeaBA, which was encoded by a gene in the lost fragment of pMEA02. MeaA shared 22% to 25% amino acid sequence identity with oxygenase components of some TC-FDMs, whereas MeaB showed no sequence identity with the reductase components of those TC-FDMs. Complementation withmeaBAin MEA3-1Mut and heterologous expression inPseudomonas putidastrain KT2440 resulted in the production of an active MEHQ monooxygenase.

scholarly journals Molecular Mechanism and Genetic Determinants of Buprofezin Degradation

2017 ◽  
Vol 83 (18) ◽  
Author(s):  
Xueting Chen ◽  
Junbin Ji ◽  
Leizhen Zhao ◽  
Jiguo Qiu ◽  
Chen Dai ◽  
...  
Keyword(s):  
Molecular Mechanism ◽  
Benzene Ring ◽  
Microbial Degradation ◽  
Natural Environment ◽  
Heterocyclic Ring ◽  
Ring Cleavage ◽  
Genetic Determinants ◽  
Catabolic Pathway ◽  
Content Type ◽  
Aromatic Ring Cleavage

ABSTRACT Buprofezin is a widely used insect growth regulator whose residue has been frequently detected in the environment, posing a threat to aquatic organisms and nontarget insects. Microorganisms play an important role in the degradation of buprofezin in the natural environment. However, the relevant catabolic pathway has not been fully characterized, and the molecular mechanism of catabolism is still completely unknown. Rhodococcus qingshengii YL-1 can utilize buprofezin as a sole source of carbon and energy for growth. In this study, the upstream catabolic pathway in strain YL-1 was identified using tandem mass spectrometry. Buprofezin is composed of a benzene ring and a heterocyclic ring. The degradation is initiated by the dihydroxylation of the benzene ring and continues via dehydrogenation, aromatic ring cleavage, breaking of an amide bond, and the release of the heterocyclic ring 2-tert-butylimino-3-isopropyl-1,3,5-thiadiazinan-4-one (2-BI). A buprofezin degradation-deficient mutant strain YL-0 was isolated. A comparative genomic analysis combined with gene deletion and complementation experiments revealed that the gene cluster bfzBA3A4A1A2C is responsible for the upstream catabolic pathway of buprofezin. The bfzA3A4A1A2 cluster encodes a novel Rieske nonheme iron oxygenase (RHO) system that is responsible for the dihydroxylation of buprofezin at the benzene ring; bfzB is involved in dehydrogenation, and bfzC is in charge of benzene ring cleavage. Furthermore, the products of bfzBA3A4A1A2C can also catalyze dihydroxylation, dehydrogenation, and aromatic ring cleavage of biphenyl, flavanone, flavone, and bifenthrin. In addition, a transcriptional study revealed that bfzBA3A4A1A2C is organized in one transcriptional unit that is constitutively expressed in strain YL-1. IMPORTANCE There is an increasing concern about the residue and environmental fate of buprofezin. Microbial metabolism is an important mechanism responsible for the buprofezin degradation in the natural environment. However, the molecular mechanism and genetic determinants of microbial degradation of buprofezin have not been well identified. This work revealed that gene cluster bfzBA3A4A1A2C is responsible for the upstream catabolic pathway of buprofezin in Rhodococcus qingshengii YL-1. The products of bfzBA3A4A1A2C could also degrade bifenthrin, a widely used pyrethroid insecticide. These findings enhance our understanding of the microbial degradation mechanism of buprofezin and benefit the application of strain YL-1 and bfzBA3A4A1A2C in the bioremediation of buprofezin contamination.

scholarly journals Isolation of the (+)-Pinoresinol-MineralizingPseudomonassp. Strain SG-MS2 and Elucidation of Its Catabolic Pathway

2017 ◽  
Vol 84 (4) ◽  
Author(s):  
Madhura Shettigar ◽  
Sahil Balotra ◽  
David Cahill ◽  
Andrew C. Warden ◽  
Michael J. Lacey ◽  
...  
Keyword(s):  
Shikimic Acid ◽  
Conclusive Evidence ◽  
Quinone Methide ◽  
Ring Cleavage ◽  
Catabolic Pathway ◽  
Content Type ◽  
Reductive Transformation ◽  
Benzylic Hydroxylation ◽  
Acid Pathway ◽  
Dead Plant

ABSTRACTPinoresinol is a dimer of two β-β′-linked coniferyl alcohol molecules. It is both a plant defense molecule synthesized through the shikimic acid pathway and a representative of several β-β-linked dimers produced during the microbial degradation of lignin in dead plant material. Until now, little has been known about the bacterial catabolism of such dimers. Here we report the isolation of the efficient (+)-pinoresinol-mineralizingPseudomonassp. strain SG-MS2 and its catabolic pathway. Degradation of pinoresinol in this strain is inducible and proceeds via a novel oxidative route, which is in contrast to the previously reported reductive transformation by other bacteria. Based on enzyme assays and bacterial growth, cell suspension, and resting cell studies, we provide conclusive evidence that pinoresinol degradation in strain SG-MS2 is initiated by benzylic hydroxylation, generating a hemiketal via a quinone methide intermediate, which is then hydrated at the benzylic carbon by water. The hemiketal, which stays in equilibrium with the corresponding keto alcohol, undergoes an aryl-alkyl cleavage to generate a lactone and 2-methoxyhydroquinone. While the fate of 2-methoxyhydroquinone is not investigated further, it is assumed to be assimilated by ring cleavage. The lactone is further metabolized via two routes, namely, lactone ring cleavage and benzylic hydroxylation via a quinone methide intermediate, as described above. The resulting hemiketal again exists in equilibrium with a keto alcohol. Our evidence suggests that both routes of lactone metabolism lead to vanillin and vanillic acid, which we show can then be mineralized by strain SG-MS2.IMPORTANCEThe oxidative catabolism of (+)-pinoresinol degradation elucidated here is fundamentally different from the reductive cometabolism reported for two previously characterized bacteria. Our findings open up new opportunities to use lignin for the biosynthesis of vanillin, a key flavoring agent in foods, beverages, and pharmaceuticals, as well as various new lactones. Our work also has implications for the study of new pinoresinol metabolites in human health. The enterodiol and enterolactone produced through reductive transformation of pinoresinol by gut microbes have already been associated with decreased risks of cancer and cardiovascular diseases. The metabolites from oxidative metabolism we find here also deserve attention in this respect.

scholarly journals The Isoenzymic Diketocamphane Monooxygenases of Pseudomonas putida ATCC 17453—An Episodic History and Still Mysterious after 60 Years

2021 ◽  
Vol 9 (12) ◽  
pp. 2593
Author(s):  
Andrew Willetts
Keyword(s):  
Pseudomonas Putida ◽  
Current Knowledge ◽  
Chemical Oxidation ◽  
Ring Cleavage ◽  
Catabolic Pathway ◽  
Naturally Occurring ◽  
Mistaken Belief ◽  
Two Component ◽  
History Of ◽  
The Many

Researching the involvement of molecular oxygen in the degradation of the naturally occurring bicyclic terpene camphor has generated a six-decade history of fascinating monooxygenase biochemistry. While an extensive bibliography exists reporting the many varied studies on camphor 5-monooxygenase, the initiating enzyme of the relevant catabolic pathway in Pseudomonas putida ATCC 17453, the equivalent recorded history of the isoenzymic diketocamphane monooxygenases, the enzymes that facilitate the initial ring cleavage of the bicyclic terpene, is both less extensive and more enigmatic. First referred to as ‘ketolactonase—an enzyme for cyclic lactonization’—the enzyme now classified as 2,5-diketocamphane 1,2-monooxygenase (EC 1.14.14.108) holds a special place in the history of oxygen-dependent biochemistry, being the first biocatalyst confirmed to undertake a biooxygenation reaction equivalent to the peracid-catalysed Baeyer–Villiger chemical oxidation first reported in the late 19th century. However, following that auspicious beginning, the biochemistry of EC 1.14.14.108, and its isoenzymic partner 3,6-diketocamphane 1,6-monooxygenase (EC 1.14.14.155) was dogged for many years by the mistaken belief that the enzymes were true flavoproteins that function with a tightly-bound flavin cofactor in the active site. This misconception led to a number of erroneous interpretations of relevant experimental data. It is only in the last decade, initially as the result of pure serendipity, that these enzymes have been confirmed to be members of a relatively recently discovered class of oxygen-dependent enzymes, the flavin-dependent two-component monooxygenases. This has promoted a renaissance of interest in the enzymes, resulting in programmes of research that have significantly expanded current knowledge of both their mode of action and regulation in camphor-grown P. putida ATCC 17453. However, some features of the biochemistry of the isoenzymic diketocamphane monooxygenases remain currently unexplained. It is the episodic history of these enzymes and some of what remains unresolved that are the principal subjects of this review.

scholarly journals Microbial Degradation of Pyridine: a Complete Pathway in Arthrobacter sp. Strain 68b Deciphered

2020 ◽  
Vol 86 (15) ◽  
Author(s):  
Vida Časaitė ◽  
Rūta Stanislauskienė ◽  
Justas Vaitekūnas ◽  
Daiva Tauraitė ◽  
Rasa Rutkienė ◽  
...  
Keyword(s):  
Gene Cluster ◽  
Ring Cleavage ◽  
Monooxygenase System ◽  
Enzymatic Reactions ◽  
Catabolic Pathway ◽  
Semialdehyde Dehydrogenase ◽  
Catabolic Plasmid ◽  
Succinate Semialdehyde ◽  
Key Enzyme ◽  
Pyridine Metabolism

ABSTRACT Pyridine and its derivatives constitute the majority of heterocyclic aromatic compounds that occur largely as a result of human activities and contribute to environmental pollution. It is known that they can be degraded by various bacteria in the environment; however, the degradation of unsubstituted pyridine has not yet been completely resolved. In this study, we present data on the pyridine catabolic pathway in Arthrobacter sp. strain 68b at the level of genes, enzymes, and metabolites. The pyr gene cluster, responsible for the degradation of pyridine, was identified in a catabolic plasmid, p2MP. The pathway of pyridine metabolism consisted of four enzymatic steps and ended by the formation of succinic acid. The first step in the degradation of pyridine proceeds through a direct ring cleavage catalyzed by a two-component flavin-dependent monooxygenase system, encoded by pyrA (pyridine monooxygenase) and pyrE genes. The genes pyrB, pyrC, and pyrD were found to encode (Z)-N-(4-oxobut-1-enyl)formamide dehydrogenase, amidohydrolase, and succinate semialdehyde dehydrogenase, respectively. These enzymes participate in the subsequent steps of pyridine degradation. The metabolites of these enzymatic reactions were identified, and this allowed us to reconstruct the entire pyridine catabolism pathway in Arthrobacter sp. 68b. IMPORTANCE The biodegradation pathway of pyridine, a notorious toxicant, is relatively unexplored, as no genetic data related to this process have ever been presented. In this paper, we describe the plasmid-borne pyr gene cluster, which includes the complete set of genes responsible for the degradation of pyridine. A key enzyme, the monooxygenase PyrA, which is responsible for the first step of the catabolic pathway, performs an oxidative cleavage of the pyridine ring without typical activation steps such as reduction or hydroxylation of the heterocycle. This work provides new insights into the metabolism of N-heterocyclic compounds in nature.

Investigating interdependencies of sustainable supplier selection criteria: an appraisal using ISM

2020 ◽  
Vol 13 (2) ◽  
pp. 195-210 ◽  
Author(s):  
Avanish Singh Chauhan ◽  
Gaurav Kumar Badhotiya ◽  
Gunjan Soni ◽  
Prem Kumari
Keyword(s):  
Supplier Selection ◽  
Selection Criteria ◽  
Local Community ◽  
Pollution Prevention ◽  
Content Type ◽  
The Past ◽  
Micmac Analysis ◽  
Sustainable Supplier Selection ◽  
Social Environmental ◽  
Practical Implications

Purpose Because of the increased global competition and the need for environment consciousness, organisations have started focusing on incorporating sustainability dimensions into suppler selection criteria. In the past decade, sustainable supplier selection has received much attention from researchers as well as industry practitioners. The purpose of this paper is to identify various sustainable supplier selection criteria (SSSC) and underlying interdependencies among prominent selection criteria to develop a framework for sustainability dimensions. Design/methodology/approach The sustainable criteria for supplier selection were established through comprehensive literature review. An interpretive structural modelling (ISM) approach is used to investigate the interrelationships among these criteria. Findings A total of 21 SSSC under 3 dimensions (social, environmental and economic) are established. Ten criteria related to quality, capability, flexibility, waste management, pollution prevention, local community, employment practice, labour, etc. are exhibiting strong driving as well as dependence power, as demonstrated through ISM and matriced’ impacts croises-multiplication applique’ and classement (MICMAC) analysis. The findings show that delivery/service, eco design and rights of stakeholders are the “key” criteria having a high-driving and low-dependence power. These criteria require high attention from managers, while other criteria having low-driving and high-dependence power require secondary actions. Research limitations/implications The inter-relations for the development of ISM model and MICMAC analysis were obtained through the opinion of industry experts and academicians, which may tend to be subjectively biased. Further exploration is proposed to statistically validate the developed interdependency model. Practical implications This paper might act as a reference for the supplier development managers of organisations by providing an appraisal of various SSSC based on their interdependencies. Originality/value This study contributes to the knowledge base by proposing a framework of the interrelationships of the SSSC and also provides an additional perspective for managing these criteria based on ISM.

FINRA’s disciplinary actions in 2017: increased restitution ordered with minimal changes in number of cases

2018 ◽  
Vol 19 (2) ◽  
pp. 19-23
Author(s):  
Brian Rubin ◽  
Adam Pollet
Keyword(s):  
Money Laundering ◽  
Design Methodology ◽  
Disciplinary Actions ◽  
Financial Industry ◽  
Electronic Communications ◽  
Content Type ◽  
The Past ◽  
Expert Analysis ◽  
Research Analysts ◽  
Practical Implications

Purpose The purpose of this paper is to analyze the Financial Industry Regulatory Authority’s (FINRA) 2017 disciplinary actions, the issues that resulted in the most significant fines and restitution and the emerging enforcement trends from 2017 and beyond. Design/methodology/approach The approach of this paper discusses the disciplinary actions in 2017 and prior years, details the top 2017 enforcement issues measured by total fines assessed, including anti-money laundering, trade reporting, electronic communications, books and records, research analysts and research reports, and explains current enforcement trends, including restitution, suitability cases and technological issues. Findings In 2017, restitution more than doubled from the prior year, resulting in the fourth highest total sanctions (fines combined with restitution and disgorgement) assessed by FINRA over the past 10 years. Practical implications Firms and their representatives should heed the trends in both the substantial restitution FINRA is ordering and the related enforcement issues in the cases FINRA has brought. Originality/value This paper provides expert analysis and guidance from experienced securities enforcement lawyers.

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