scholarly journals Protein Engineering of the Archetypal Nitroarene Dioxygenase of Ralstonia sp. Strain U2 for Activity on Aminonitrotoluenes and Dinitrotoluenes through Alpha-Subunit Residues Leucine 225, Phenylalanine 350, and Glycine 407

2005 ◽  
Vol 187 (10) ◽  
pp. 3302-3310 ◽  
Author(s):  
Brendan G. Keenan ◽  
Thammajun Leungsakul ◽  
Barth F. Smets ◽  
Masa-aki Mori ◽  
David E. Henderson ◽  
...  
Keyword(s):  
Random Mutagenesis ◽  
Nitroaromatic Compounds ◽  
Heme Iron ◽  
Alpha Subunit ◽  
Saturation Mutagenesis ◽  
Dna Shuffling ◽  
Wild Type ◽  
Α Subunit ◽  
Non Heme Iron ◽  
Nitrobenzyl Alcohol

ABSTRACT Naphthalene dioxygenase (NDO) from Ralstonia sp. strain U2 has not been reported to oxidize nitroaromatic compounds. Here, saturation mutagenesis of NDO at position F350 of the α-subunit (NagAc) created variant F350T that produced 3-methyl-4-nitrocatechol from 2,6-dinitrotoluene (26DNT), that released nitrite from 23DNT sixfold faster than wild-type NDO, and that produced 3-amino-4-methyl-5-nitrocatechol and 2-amino-4,6-dinitrobenzyl alcohol from 2-amino-4,6-dinitrotoluene (2A46DNT) (wild-type NDO has no detectable activity on 26DNT and 2A46DNT). DNA shuffling identified the beneficial NagAc mutation G407S, which when combined with the F350T substitution, increased the rate of NDO oxidation of 26DNT, 23DNT, and 2A46DNT threefold relative to variant F350T. DNA shuffling of NDO nagAcAd also generated the NagAc variant G50S/L225R/A269T with an increased rate of 4-amino-2-nitrotoluene (4A2NT; reduction product of 2,4-dinitrotoluene) oxidation; from 4A2NT, this variant produced both the previously uncharacterized oxidation product 4-amino-2-nitrocresol (enhanced 11-fold relative to wild-type NDO) as well as 4-amino-2-nitrobenzyl alcohol (4A2NBA; wild-type NDO does not generate this product). G50S/L225R/A269T also had increased nitrite release from 23DNT (14-fold relative to wild-type NDO) and generated 2,3-dinitrobenzyl alcohol (23DNBA) fourfold relative to wild-type NDO. The importance of position L225 for catalysis was confirmed through saturation mutagenesis; relative to wild-type NDO, NDO variant L225R had 12-fold faster generation of 4-amino-2-nitrocresol and production of 4A2NBA from 4A2NT as well as 24-fold faster generation of nitrite and 15-fold faster generation of 23DNBA from 23DNT. Hence, random mutagenesis discovered two new residues, G407 and L225, that influence the regiospecificity of Rieske non-heme-iron dioxygenases.

scholarly journals Protein Engineering of Toluene-o-Xylene Monooxygenase from Pseudomonas stutzeri OX1 for Synthesizing 4-Methylresorcinol, Methylhydroquinone, and Pyrogallol

2004 ◽  
Vol 70 (6) ◽  
pp. 3253-3262 ◽  
Author(s):  
G�n�l Vardar ◽  
Thomas K. Wood
Keyword(s):  
Active Site ◽  
High Performance ◽  
Agar Plate ◽  
Pseudomonas Stutzeri ◽  
Saturation Mutagenesis ◽  
Dna Shuffling ◽  
Natural Substrate ◽  
Wild Type ◽  
Active Site Residues ◽  
Derivatives Of

ABSTRACT Toluene-o-xylene monooxygenase (ToMO) from Pseudomonas stutzeri OX1 oxidizes toluene to 3- and 4-methylcatechol and oxidizes benzene to form phenol; in this study ToMO was found to also form catechol and 1,2,3-trihydroxybenzene (1,2,3-THB) from phenol. To synthesize novel dihydroxy and trihydroxy derivatives of benzene and toluene, DNA shuffling of the alpha-hydroxylase fragment of ToMO (TouA) and saturation mutagenesis of the TouA active site residues I100, Q141, T201, and F205 were used to generate random mutants. The mutants were initially identified by screening with a rapid agar plate assay and then were examined further by high-performance liquid chromatography and gas chromatography. Several regiospecific mutants with high rates of activity were identified; for example, Escherichia coli TG1/pBS(Kan)ToMO expressing the F205G TouA saturation mutagenesis variant formed 4-methylresorcinol (0.78 nmol/min/mg of protein), 3-methylcatechol (0.25 nmol/min/mg of protein), and methylhydroquinone (0.088 nmol/min/mg of protein) from o-cresol, whereas wild-type ToMO formed only 3-methylcatechol (1.1 nmol/min/mg of protein). From o-cresol, the I100Q saturation mutagenesis mutant and the M180T/E284G DNA shuffling mutant formed methylhydroquinone (0.50 and 0.19 nmol/min/mg of protein, respectively) and 3-methylcatechol (0.49 and 1.5 nmol/min/mg of protein, respectively). The F205G mutant formed catechol (0.52 nmol/min/mg of protein), resorcinol (0.090 nmol/min/mg of protein), and hydroquinone (0.070 nmol/min/mg of protein) from phenol, whereas wild-type ToMO formed only catechol (1.5 nmol/min/mg of protein). Both the I100Q mutant and the M180T/E284G mutant formed hydroquinone (1.2 and 0.040 nmol/min/mg of protein, respectively) and catechol (0.28 and 2.0 nmol/min/mg of protein, respectively) from phenol. Dihydroxybenzenes were further oxidized to trihydroxybenzenes with different regiospecificities; for example, the I100Q mutant formed 1,2,4-THB from catechol, whereas wild-type ToMO formed 1,2,3-THB (pyrogallol). Regiospecific oxidation of the natural substrate toluene was also checked; for example, the I100Q mutant formed 22% o-cresol, 44% m-cresol, and 34% p-cresol, whereas wild-type ToMO formed 32% o-cresol, 21% m-cresol, and 47% p-cresol.

scholarly journals Saturation Mutagenesis of Toluene ortho-Monooxygenase of Burkholderia cepacia G4 for Enhanced 1-Naphthol Synthesis and Chloroform Degradation

2004 ◽  
Vol 70 (6) ◽  
pp. 3246-3252 ◽  
Author(s):  
Lingyun Rui ◽  
Young Man Kwon ◽  
Ayelet Fishman ◽  
Kenneth F. Reardon ◽  
Thomas K. Wood
Keyword(s):  
Burkholderia Cepacia ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Saturation Mutagenesis ◽  
Wild Type ◽  
Oxidation Activity ◽  
Α Subunit ◽  
Whole Cells ◽  
Elevated Expression ◽  
Naphthalene Oxidation

ABSTRACT Directed evolution of toluene ortho-monooxygenase (TOM) of Burkholderia cepacia G4 previously created the hydroxylase α-subunit (TomA3) V106A variant (TOM-Green) with increased activity for both trichloroethylene degradation (twofold enhancement) and naphthalene oxidation (six-times-higher activity). In the present study, saturation mutagenesis was performed at position A106 with Escherichia coli TG1/pBS(Kan)TOMV106A to improve TOM activity for both chloroform degradation and naphthalene oxidation. Whole cells expressing the A106E variant had two times better naphthalene-to-1-naphthol activity than the wild-type cells (V max of 9.3 versus 4.5 nmol � min−1 � mg of protein−1 and unchanged Km ), and the regiospecificity of the A106E variant was unchanged, with 98% 1-naphthol formed, as was confirmed with high-pressure liquid chromatography. The A106E variant degrades its natural substrate toluene 63% faster than wild-type TOM does (2.12 � 0.07 versus 1.30 � 0.06 nmol � min−1 � mg of protein−1 [mean � standard deviation]) at 91 μM and has a substantial decrease in regiospecificity, since o-cresol (50%), m-cresol (25%), and p-cresol (25%) are formed, in contrast to the 98% o-cresol formed by wild-type TOM. The A106E variant also has an elevated expression level compared to that of wild-type TOM, as evidenced by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Another variant, the A106F variant, has 2.8-times-better chloroform degradation activity based on gas chromatography (V max of 2.61 versus 0.95 nmol � min−1 � mg of protein−1 and unchanged Km ) and chloride release (0.034 � 0.002 versus 0.012 � 0.001 nmol � min−1 � mg of protein−1). The A106F variant also was expressed at levels similar to those of wild-type TOM and 62%-better toluene oxidation activity than wild-type TOM (2.11 � 0.3 versus 1.30 � 0.06 nmol � min−1 � mg of protein−1). A shift in regiospecificity of toluene hydroxylation was also observed for the A106F variant, with o-cresol (28%), m-cresol (18%), and p-cresol (54%) being formed. Statistical analysis was used to estimate that 292 colonies must be screened for a 99% probability that all 64 codons were sampled during saturation mutagenesis.

scholarly journals Protein Engineering of Epoxide Hydrolase from Agrobacterium radiobacter AD1 for Enhanced Activity and Enantioselective Production of (R)-1-Phenylethane-1,2-Diol

2005 ◽  
Vol 71 (7) ◽  
pp. 3995-4003 ◽  
Author(s):  
Lingyun Rui ◽  
Li Cao ◽  
Wilfred Chen ◽  
Kenneth F. Reardon ◽  
Thomas K. Wood
Keyword(s):  
Active Site ◽  
Epoxide Hydrolase ◽  
Styrene Oxide ◽  
Saturation Mutagenesis ◽  
Dna Shuffling ◽  
Wild Type ◽  
Wild Type Enzyme ◽  
Agrobacterium Radiobacter ◽  
Enantiomeric Ratio ◽  
Enhanced Activity

ABSTRACT DNA shuffling and saturation mutagenesis of positions F108, L190, I219, D235, and C248 were used to generate variants of the epoxide hydrolase of Agrobacterium radiobacter AD1 (EchA) with enhanced enantioselectivity and activity for styrene oxide and enhanced activity for 1,2-epoxyhexane and epoxypropane. EchA variant I219F has more than fivefold-enhanced enantioselectivity toward racemic styrene oxide, with the enantiomeric ratio value (E value) for the production of (R)-1-phenylethane-1,2-diol increased from 17 for the wild-type enzyme to 91, as well as twofold-improved activity for the production of (R)-1-phenylethane-1,2-diol (1.96 ± 0.09 versus 1.04 ± 0.07 μmol/min/mg for wild-type EchA). Computer modeling indicated that this mutation significantly alters (R)-styrene oxide binding in the active site. Another three variants from EchA active-site engineering, F108L/C248I, I219L/C248I, and F108L/I219L/C248I, also exhibited improved enantioselectivity toward racemic styrene oxide in favor of production of the corresponding diol in the (R) configuration (twofold enhancement in their E values). Variant F108L/I219L/C248I also demonstrated 10-fold- and 2-fold-increased activity on 5 mM epoxypropane (24 ± 2 versus 2.4 ± 0.3 μmol/min/mg for the wild-type enzyme) and 5 mM 1,2-epoxyhexane (5.2 ± 0.5 versus 2.6 ± 0.0 μmol/min/mg for the wild-type enzyme). Both variants L190F (isolated from a DNA shuffling library) and L190Y (created from subsequent saturation mutagenesis) showed significantly enhanced activity for racemic styrene oxide hydrolysis, with 4.8-fold (8.6 ± 0.3 versus 1.8 ± 0.2 μmol/min/mg for the wild-type enzyme) and 2.7-fold (4.8 ± 0.8 versus 1.8 ± 0.2 μmol/min/mg for the wild-type enzyme) improvements, respectively. L190Y also hydrolyzed 1,2-epoxyhexane 2.5 times faster than the wild-type enzyme.

scholarly journals Protein Engineering of a Nitrilase from Burkholderia cenocepacia J2315 for Efficient and Enantioselective Production of (R)-o-Chloromandelic Acid

2015 ◽  
Vol 81 (24) ◽  
pp. 8469-8477 ◽  
Author(s):  
Hualei Wang ◽  
Wenyuan Gao ◽  
Huihui Sun ◽  
Lifeng Chen ◽  
Lujia Zhang ◽  
...  
Keyword(s):  
Protein Engineering ◽  
Hot Spots ◽  
Enantiomeric Excess ◽  
Random Mutagenesis ◽  
Burkholderia Cenocepacia ◽  
Saturation Mutagenesis ◽  
Wild Type ◽  
High Concentration ◽  
Content Type ◽  
Optically Pure

ABSTRACTThe nitrilase-mediated pathway has significant advantages in the production of optically pure aromatic α-hydroxy carboxylic acids. However, low enantioselectivity and activity are observed on hydrolyzingo-chloromandelonitrile to produce optically pure (R)-o-chloromandelic acid. In the present study, a protein engineering approach was successfully used to enhance the performance of nitrilase obtained fromBurkholderia cenocepaciastrain J2315 (BCJ2315) in hydrolyzingo-chloromandelonitrile. Four hot spots (T49, I113, Y199, and T310) responsible for the enantioselectivity and activity of BCJ2315 were identified by random mutagenesis. An effective double mutant (I113M/Y199G [encoding the replacement of I with M at position 113 and Y with G at position 199]), which demonstrated remarkably enhanced enantioselectivity (99.1% enantiomeric excess [ee] compared to 89.2%eefor the wild type) and relative activity (360% of the wild type), was created by two rounds of site saturation mutagenesis, first at each of the four hot spots and subsequently at position 199 for combination with the selected beneficial mutation I113M. Notably, this mutant also demonstrated dramatically enhanced enantioselectivity and activity toward other mandelonitrile derivatives and, thus, broadened the substrate scope of this nitrilase. Using an ethyl acetate-water (1:9) biphasic system,o-chloromandelonitrile (500 mM) was completely hydrolyzed in 3 h by this mutant with a small amount of biocatalyst (10 g/liter wet cells), resulting in a high concentration of (R)-o-chloromandelic acid with 98.7%ee, to our knowledge the highest ever reported. This result highlights a promising method for industrial production of optically pure (R)-o-chloromandelic acid. Insight into the source of enantioselectivity and activity was gained by homology modeling and molecular docking experiments.

Tmprss6 Is a Genetic Modifier of the Hfe-Hemochromatosis Phenotype in Mice.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 625-625
Author(s):  
Karin E. Finberg ◽  
Rebecca Whittlesey ◽  
Mark D. Fleming ◽  
Nancy C. Andrews
Keyword(s):  
Iron Deficiency ◽  
Iron Content ◽  
Serum Iron ◽  
Iron Concentration ◽  
Transferrin Saturation ◽  
Heme Iron ◽  
Deficiency Anemia ◽  
Wild Type ◽  
Non Heme Iron ◽  
Serum Iron Concentration

Abstract Abstract 625 HFE-associated hereditary hemochromatosis is an autosomal recessive disorder characterized by inappropriately elevated absorption of dietary iron by the gastrointestinal mucosa, resulting in excessive storage of iron in multiple organs. A significant proportion of individuals who are homozygous for HFE mutations fail to develop clinical symptoms, suggesting that environmental and/or genetic factors may influence the penetrance of this disorder. In vitro and animal studies have revealed that HFE promotes the expression of hepcidin, a circulating hormone produced by the liver that acts to inhibit iron absorption by the duodenum. In contrast, TMPRSS6, a transmembrane serine protease produced by the liver, acts to inhibit hepcidin expression; both humans and mice harboring TMPRSS6 mutations display impaired intestinal iron absorption, resulting in a phenotype of iron-refractory iron deficiency anemia (IRIDA). Here we asked if heterozygous or homozygous loss of Tmprss6 function could modify the iron overload phenotype of Hfe null (Hfe-/-) mice, a mouse model of human HFE-hemochromatosis. To test this, we bred Hfe-/- mice to Tmprss6-/- mice; the latter harbor a targeted disruption of the Tmprss6 serine protease domain and exhibit an IRIDA phenotype. We generated Hfe-/-Tmprss6+/+, Hfe-/-Tmprss6+/-, and Hfe-/-Tmprss6-/- female mice (6-10 mice per genotype), in which parameters of systemic iron homeostasis were compared at eight weeks of age by Student's t test. Consistent with previous study of Hfe-/- mice, Hfe-/- mice harboring two wild type Tmprss6 alleles (Hfe-/-Tmprss6+/+ mice) showed serum iron concentration, transferrin saturation, and hepatic non-heme iron content that were significantly elevated compared to wild type mice of similar genetic background. Heterozygosity for Tmprss6 mutation, however, markedly reduced the severity of the hemochromatosis phenotype of Hfe-/- mice. Compared to Hfe-/- mice with two wild type Tmprss6 alleles, Hfe-/- mice that were heterozygous for Tmprss6 mutation (Hfe-/-Tmprss6+/- mice) showed significant reductions in serum iron concentration (p<0.01), transferrin saturation (p<0.005), and non-heme iron content of liver (p<10-4). Furthermore, homozygosity for Tmprss6 mutation completely ameliorated the iron overload phenotype of Hfe-/- mice and in fact led to systemic iron deficiency. Compared to both Hfe-/-Tmprss6+/+ and Hfe-/-Tmprss6+/- mice, Hfe-/-Tmprss6-/- mice showed markedly reduced serum iron concentration (p<10-7), transferrin saturation (p<10-10), and non-heme iron content of liver (p<10-4). Hfe-/-Tmprss6-/- mice also displayed iron deficiency anemia and appeared phenotypically similar to previously characterized Tmprss6-/- mice harboring two wild type copies of Hfe. In summary, these results demonstrate that Tmprss6 is a genetic modifier of the Hfe-hemochromatosis phenotype in mice. These findings suggest that natural genetic variation in the human ortholog TMPRSS6 might modify the clinical penetrance of HFE-hemochromatosis and raise the possibility that pharmacological inhibition of TMPRSS6 activity might prove an effective therapy in this disorder. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Laboratory Evolution of Toluene Dioxygenase To Accept 4-Picoline as a Substrate

2001 ◽  
Vol 67 (9) ◽  
pp. 3882-3887 ◽  
Author(s):  
Takeshi Sakamoto ◽  
John M. Joern ◽  
Akira Arisawa ◽  
Frances H. Arnold
Keyword(s):  
Escherichia Coli ◽  
Directed Evolution ◽  
Stop Codon ◽  
Random Mutagenesis ◽  
Product Formation ◽  
Saturation Mutagenesis ◽  
Wild Type ◽  
Laboratory Evolution ◽  
Toluene Dioxygenase ◽  
Naturally Occurring

ABSTRACT We are using directed evolution to extend the range of dioxygenase-catalyzed biotransformations to include substrates that are either poorly accepted or not accepted at all by the naturally occurring enzymes. Here we report on the oxidation of a heterocyclic substrate, 4-picoline, by toluene dioxygenase (TDO) and improvement of the enzyme's activity by laboratory evolution. The biotransformation of 4-picoline proceeds at only ∼4.5% of the rate of the natural reaction on toluene. Random mutagenesis, saturation mutagenesis, and screening directly for product formation using a modified Gibbs assay generated mutant TDO 3-B38, in which the wild-type stop codon was replaced with a codon encoding threonine. Escherichia coli-expressed TDO 3-B38 exhibited 5.6 times higher activity toward 4-picoline and ∼20% more activity towards toluene than wild-type TDO. The product of the biotransformation of 4-picoline is 3-hydroxy-4-picoline; no cis-diols of 4-picoline were observed.

Tmprss6, An Inhibitor of Hepatic Bmp/Smad Signaling, Is Required for Hepcidin Suppression and Iron Loading In a Mouse Model of β-Thalassemia

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 164-164
Author(s):  
Karin E. Finberg ◽  
Rebecca L. Whittlesey ◽  
Stefano Rivella ◽  
Nancy C. Andrews
Keyword(s):  
Iron Deficiency ◽  
Iron Homeostasis ◽  
Heme Iron ◽  
Mrna Levels ◽  
Iron Loading ◽  
Wild Type ◽  
Smad Signaling ◽  
Hepcidin Expression ◽  
Non Heme Iron ◽  
Hepcidin Mrna

Abstract Abstract 164 TMPRSS6, a transmembrane protease produced by the liver, is an essential regulator of mammalian iron homeostasis. TMPRSS6 inhibits the expression of hepcidin, a circulating peptide that decreases intestinal iron absorption and macrophage iron release, by down-regulating hepatic BMP/SMAD signaling for hepcidin production. Accordingly, TMPRSS6 mutations result in elevated hepcidin levels, impaired absorption of dietary iron, and systemic iron deficiency. Interestingly, in congenital iron loading anemias such as β-thalassemia, hepcidin levels are inappropriately low relative to body iron stores, a finding that has been postulated to result from the production of a hepcidin-repressing factor in the setting of ineffective erythropoiesis. Here we asked if Tmprss6 is required to achieve the hepcidin suppression present in Hbbth3/+ mice, a model of β-thalassemia intermedia. To test this, we bred Hbbth3/+ mice to mice harboring a targeted disruption of the Tmprss6 serine protease domain. We generated mice of various Hbb-Tmprss6 genotype combinations and compared parameters of systemic iron homeostasis at 8 weeks of age. Consistent with prior studies of Hbbth3/+ mice, Hbbth3/+ mice harboring 2 wild-type Tmprss6 alleles (Hbbth3/+Tmprss6+/+ mice) showed non-heme iron concentrations of liver, spleen, and kidney that were significantly elevated compared to wild-type controls. Homozygosity for Tmprss6 mutation, however, ameliorated the iron overload phenotype of Hbbth3/+ mice and led to systemic iron deficiency. Tissue non-heme iron concentrations were markedly reduced in Hbbth3/+Tmprss6−/− mice as compared to Hbbth3/+Tmprss6+/+ mice and were similar to levels observed in Tmprss6−/− mice harboring 2 wild-type Hbb alleles. Hbbth3/+Tmprss6−/− mice had hemoglobin levels similar to the thalassemic levels present in Hbbth3/+Tmprss6+/+ mice. However, compared to Hbbth3/+Tmprss6+/+ mice, Hbbth3/+Tmprss6−/− mice showed markedly reduced erythrocyte mean corpuscular volume and serum transferrin saturation, as well as increased red blood cell count. Interestingly, homozygous loss of Tmprss6 in Hbbth3/+ mice also led to marked reduction in splenomegaly and improvement in peripheral red blood cell morphology. Consistent with prior studies of Hbbth3/+ mice, Hbbth3/+Tmprss6+/+ mice displayed hepatic hepcidin mRNA levels that were similar to wild-type and were, therefore, inappropriately decreased relative to their increased hepatic iron stores. Hepatic mRNA levels of Bmp6, encoding a Bmp ligand that is transcriptionally regulated by iron and acts as a key regulator of hepcidin expression in vivo, were significantly elevated in Hbbth3/+Tmprss6+/+ mice, suggesting that their relative hepcidin deficiency does not result from impaired Bmp6 transcription. While Hbbth3/+Tmprss6+/+ mice showed suppressed hepcidin levels, homozygous loss of Tmprss6 alleviated their hepcidin suppression and led to elevated hepcidin mRNA levels similar to Tmprss6−/− mice harboring 2 wild-type Hbb alleles. Hbbth3/+Tmprss6−/− mice also showed elevated hepatic mRNA encoding Id1, another transcriptional target of Bmp/Smad signaling. These findings indicate that Tmprss6 is required to achieve the suppression of hepatic hepcidin expression that underlies systemic iron overload in Hbbth3/+ mice. Furthermore, our results demonstrate that, by up-regulating hepatic Bmp/Smad signaling for hepcidin production, genetic loss of Tmprss6 induces profound changes in systemic iron homeostasis in this thalassemia model. Disclosures: No relevant conflicts of interest to declare.

Location of the Non-Heme Iron Center on the α Subunit of Photoreactive Nitrile Hydratase fromRhodococcussp. N-771

1996 ◽  
Vol 221 (1) ◽  
pp. 146-150 ◽  
Author(s):  
Masafumi Odaka ◽  
Takumi Noguchi ◽  
Shigehiro Nagashima ◽  
Masafumi Yohda ◽  
Sadayo Yabuki ◽  
...  
Keyword(s):  
Nitrile Hydratase ◽  
Heme Iron ◽  
Α Subunit ◽  
Non Heme Iron ◽  
Iron Center
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