scholarly journals Peptidylglycine α-amidating monooxygenase as a therapeutic target or biomarker

2021 ◽  
Author(s):  
David Merkler ◽  
Aidan Hawley ◽  
Betty Eipper ◽  
Richard Mains
Keyword(s):  
Biosynthetic Pathway ◽  
Homo Sapiens ◽  
Growth Promoters ◽  
Therapeutic Value ◽  
Amidation Reaction ◽  
Peptide Biosynthesis ◽  
Membrane Bound ◽  
Peptide Secretion ◽  
Amidated Peptide ◽  
Rate Limiting

Peptides play a key role in controlling many physiological and neurobiological pathways. Many bioactive peptides require a C-terminal α-amide for full activity. The bifunctional enzyme catalyzing α-amidation, peptidylglycine α-amidating monooxygenase (PAM), is the sole enzyme responsible for amidated peptide biosynthesis, from Chlamydomonas reinhardtii to Homo sapiens. Many neuronal and endocrine functions are dependent upon amidated peptides; additional amidated peptides are growth promoters in tumors. The amidation reaction occurs in two steps, glycine α-hydroxylation followed by dealkylation to generate the α-amide product. Currently, most potentially useful inhibitors target the first reaction, which is rate-limiting. PAM is a membrane-bound enzyme that visits the cell surface during peptide secretion. PAM is then used again in the biosynthetic pathway, meaning that cell-impermeable inhibitors or inactivators could have therapeutic value for the treatment of cancer or psychiatric abnormalities. To date, inhibitor design has not fully exploited the structures and mechanistic details of PAM.

scholarly journals Recognized and Emerging Features of Erythropoietic and X-Linked Protoporphyria

Diagnostics ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 151
Author(s):  
Elena Di Pierro ◽  
Francesca Granata ◽  
Michele De Canio ◽  
Mariateresa Rossi ◽  
Andrea Ricci ◽  
...  
Keyword(s):  
Biosynthetic Pathway ◽  
Aminolevulinic Acid ◽  
Protoporphyrin Ix ◽  
Limiting Factor ◽  
Zinc Protoporphyrin ◽  
Complete Understanding ◽  
Inherited Disorders ◽  
Rate Limiting ◽  
Systemic Accumulation ◽  
Made In

Erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP) are inherited disorders resulting from defects in two different enzymes of the heme biosynthetic pathway, i.e., ferrochelatase (FECH) and delta-aminolevulinic acid synthase-2 (ALAS2), respectively. The ubiquitous FECH catalyzes the insertion of iron into the protoporphyrin ring to generate the final product, heme. After hemoglobinization, FECH can utilize other metals like zinc to bind the remainder of the protoporphyrin molecules, leading to the formation of zinc protoporphyrin. Therefore, FECH deficiency in EPP limits the formation of both heme and zinc protoporphyrin molecules. The erythroid-specific ALAS2 catalyses the synthesis of delta-aminolevulinic acid (ALA), from the union of glycine and succinyl-coenzyme A, in the first step of the pathway in the erythron. In XLP, ALAS2 activity increases, resulting in the amplified formation of ALA, and iron becomes the rate-limiting factor for heme synthesis in the erythroid tissue. Both EPP and XLP lead to the systemic accumulation of protoporphyrin IX (PPIX) in blood, erythrocytes, and tissues causing the major symptom of cutaneous photosensitivity and several other less recognized signs that need to be considered. Although significant advances have been made in our understanding of EPP and XLP in recent years, a complete understanding of the factors governing the variability in clinical expression and the severity (progression) of the disease remains elusive. The present review provides an overview of both well-established facts and the latest findings regarding these rare diseases.

scholarly journals Antileishmanial Effect of 3-Aminooxy-1-Aminopropane Is Due to Polyamine Depletion

2006 ◽  
Vol 51 (2) ◽  
pp. 528-534 ◽  
Author(s):  
Sushma Singh ◽  
Angana Mukherjee ◽  
Alex R. Khomutov ◽  
Lo Persson ◽  
Olle Heby ◽  
...  
Keyword(s):  
Biosynthetic Pathway ◽  
Leishmania Donovani ◽  
Clinical Isolates ◽  
Growth And Survival ◽  
Antiproliferative Effects ◽  
Cell Growth And Differentiation ◽  
First Time ◽  
Rate Limiting ◽  
Sodium Antimony Gluconate

ABSTRACT The polyamines putrescine, spermidine, and spermine are organic cations that are required for cell growth and differentiation. Ornithine decarboxylase (ODC), the first and rate-limiting enzyme in the polyamine biosynthetic pathway, catalyzes the conversion of ornithine to putrescine. As the polyamine biosynthetic pathway is essential for the growth and survival of Leishmania donovani, the causative agent of visceral leishmaniasis, inhibition of the pathway is an important leishmaniacidal strategy. In the present study, we examined for the first time the effects of 3-aminooxy-1-aminopropane (APA), an ODC inhibitor, on the growth of L. donovani. APA inhibited the growth of both promastigotes in vitro and amastigotes in the macrophage model, with the 50% inhibitory concentrations being 42 and 5 μM, respectively. However, concentrations of APA up to 200 μM did not affect the viability of macrophages. The effects of APA were completely abolished by the addition of putrescine or spermidine. APA induced a significant decrease in ODC activity and putrescine, spermidine, and trypanothione levels in L. donovani promastigotes. Parasites were transfected with an episomal ODC construct, and these ODC overexpressers exhibited significant resistance to APA and were concomitantly resistant to sodium antimony gluconate (Pentostam), indicating a role for ODC overexpression in antimonial drug resistance. Clinical isolates with sodium antimony gluconate resistance were also found to overexpress ODC and to have significant increases in putrescine and spermidine levels. However, no increase in trypanothione levels was observed. The ODC overexpression in these clinical isolates alleviated the antiproliferative effects of APA. Collectively, our results demonstrate that APA is a potent inhibitor of L. donovani growth and that its leishmaniacidal effect is due to inhibition of ODC.

Plastoquinone-9 biosynthesis in cyanobacteria differs from that in plants and involves a novel 4-hydroxybenzoate solanesyltransferase

2012 ◽  
Vol 442 (3) ◽  
pp. 621-629 ◽  
Author(s):  
Radin Sadre ◽  
Christian Pfaff ◽  
Stephan Buchkremer
Keyword(s):  
Biosynthetic Pathway ◽  
In Vitro Assays ◽  
Transport Chain ◽  
In Vivo Labelling ◽  
Membrane Bound ◽  
Transformation Processes ◽  
Synechocystis Sp

PQ-9 (plastoquinone-9) has a central role in energy transformation processes in cyanobacteria by mediating electron transfer in both the photosynthetic as well as the respiratory electron transport chain. The present study provides evidence that the PQ-9 biosynthetic pathway in cyanobacteria differs substantially from that in plants. We identified 4-hydroxybenzoate as being the aromatic precursor for PQ-9 in Synechocystis sp. PCC6803, and in the present paper we report on the role of the membrane-bound 4-hydroxybenzoate solanesyltransferase, Slr0926, in PQ-9 biosynthesis and on the properties of the enzyme. The catalytic activity of Slr0926 was demonstrated by in vivo labelling experiments in Synechocystis sp., complementation studies in an Escherichia coli mutant with a defect in ubiquinone biosynthesis, and in vitro assays using the recombinant as well as the native enzyme. Although Slr0926 was highly specific for the prenyl acceptor substrate 4-hydroxybenzoate, it displayed a broad specificity with regard to the prenyl donor substrate and used not only solanesyl diphosphate, but also a number of shorter-chain prenyl diphosphates. In combination with in silico data, our results indicate that Slr0926 evolved from bacterial 4-hydroxybenzoate prenyltransferases catalysing prenylation in the course of ubiquinone biosynthesis.

scholarly journals Highly Diverged Homologs of Saccharomyces cerevisiae Mitochondrial mRNA-Specific Translational Activators Have Orthologous Functions in Other Budding Yeasts

Genetics ◽  
2000 ◽  
Vol 154 (3) ◽  
pp. 999-1012 ◽  
Author(s):  
Maria C Costanzo ◽  
Nathalie Bonnefoy ◽  
Elizabeth H Williams ◽  
G Desmond Clark-Walker ◽  
Thomas D Fox
Keyword(s):  
Gene Expression ◽  
Saccharomyces Cerevisiae ◽  
Kluyveromyces Lactis ◽  
Activator Proteins ◽  
Saccharomyces Kluyveri ◽  
Membrane Bound ◽  
Translational Activator ◽  
Untranslated Leaders ◽  
Rate Limiting ◽  
Pet Genes

Abstract Translation of mitochondrially coded mRNAs in Saccharomyces cerevisiae depends on membrane-bound mRNA-specific activator proteins, whose targets lie in the mRNA 5′-untranslated leaders (5′-UTLs). In at least some cases, the activators function to localize translation of hydrophobic proteins on the inner membrane and are rate limiting for gene expression. We searched unsuccessfully in divergent budding yeasts for orthologs of the COX2- and COX3-specific translational activator genes, PET111, PET54, PET122, and PET494, by direct complementation. However, by screening for complementation of mutations in genes adjacent to the PET genes in S. cerevisiae, we obtained chromosomal segments containing highly diverged homologs of PET111 and PET122 from Saccharomyces kluyveri and of PET111 from Kluyveromyces lactis. All three of these genes failed to function in S. cerevisiae. We also found that the 5′-UTLs of the COX2 and COX3 mRNAs of S. kluyveri and K. lactis have little similarity to each other or to those of S. cerevisiae. To determine whether the PET111 and PET122 homologs carry out orthologous functions, we deleted them from the S. kluyveri genome and deleted PET111 from the K. lactis genome. The pet111 mutations in both species prevented COX2 translation, and the S. kluyveri pet122 mutation prevented COX3 translation. Thus, while the sequences of these translational activator proteins and their 5′-UTL targets are highly diverged, their mRNA-specific functions are orthologous.

scholarly journals Catalytic Mechanism of the Colistin Resistance Protein MCR-1

2020 ◽  
Author(s):  
Reynier Suardiaz ◽  
Emily Lythell ◽  
Philip Hinchliffed ◽  
Marc van der Kamp ◽  
James Spencer ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Lipid A ◽  
Catalytic Mechanism ◽  
Second Step ◽  
Colistin Resistance ◽  
Membrane Bound ◽  
Resistance Protein ◽  
Phosphoethanolamine Transferases ◽  
Bacterial Lipid ◽  
Rate Limiting

<div> <div> <div> <p>The mcr-1 gene encodes a membrane-bound Zn2+-metalloenzyme, MCR-1, which catalyzes phosphoethanolamine transfer onto bacterial lipid A, making bacteria resistant to colistin, a last-resort antibiotic. Mechanistic understanding of this process remains incomplete. Here, we investigate possible catalytic pathways using DFT and ab initio calculations on cluster models and identify a complete two-step reaction mechanism. The first step, formation of a covalent phosphointermediate via trans-fer of phosphoethanolamine from a membrane phospholipid donor to the acceptor Thr285, is rate-limiting and proceeds with a single Zn2+ ion. The second step, transfer of the phosphoethanolamine group to lipid A, requires an additional Zn2+. The calculations suggest the involment of the Zn2+ orbitals directly in the reaction is limited, with the second Zn2+ acting to bind incoming lipid A and direct phosphoethanolamine addition. The new level of mechanistic detail obtained here, which distinguishes these enzymes from other phosphotransferases, will aid in the development of inhibitors specific to MCR-1 and related bacterial phosphoethanolamine transferases. </p> </div> </div> </div>

scholarly journals Dynamics of sphingolipids and the serine-palmitoyltransferase complex in oligodendrocytes during myelination

2020 ◽  
Author(s):  
Deanna L. Davis ◽  
Usha Mahawar ◽  
Victoria S. Pope ◽  
Jeremy Allegood ◽  
Carmen Sato-Bigbee ◽  
...  
Keyword(s):  
Biosynthetic Pathway ◽  
Serine Palmitoyltransferase ◽  
Neuronal Function ◽  
Peak Period ◽  
Catalytic Subunits ◽  
Rate Limiting Step ◽  
The Central Nervous System ◽  
Acyl Chains ◽  
Critical Components ◽  
Rate Limiting

AbstractMyelin is a unique, lipid-rich membrane structure that accelerates neurotransmission and supports neuronal function. Sphingolipids are critical components of myelin. Here we examined sphingolipid synthesis during the peak period of myelination in the postnatal rat brain. Importantly, we made measurements in isolated oligodendrocytes, the myelin-producing cells in the central nervous system. We analyzed sphingolipid distribution and levels of critical enzymes and regulators in the sphingolipid biosynthetic pathway, with a focus on the serine palmitoyltransferase (SPT) complex, the rate-limiting step in this pathway. During myelination levels of the major SPT subunits increased and oligodendrocyte maturation was accompanied by extensive alterations in the composition of the SPT complex. These included changes in the relative levels of alternate catalytic subunits, SPTLC2 and −3, the relative levels of isoforms of the small subunits ssSPTa and –b, and in the isoform distribution of the SPT regulators, the ORMDLs. As myelination progressed there were distinct changes in both the nature of the sphingoid backbone and the N-acyl chains incorporated into sphingolipids. The distribution of these changes among sphingolipid family members indicates that there is selective channeling of the ceramide backbone towards specific downstream metabolic pathways during myelination.

scholarly journals Hyaluronic acid fuels pancreatic cancer cell growth

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Peter K Kim ◽  
Christopher J Halbrook ◽  
Samuel A Kerk ◽  
Megan Radyk ◽  
Stephanie Wisner ◽  
...  
Keyword(s):  
Hyaluronic Acid ◽  
Biosynthetic Pathway ◽  
Human Tumor ◽  
Pancreatic Tumors ◽  
Cancer Cell Growth ◽  
Hexosamine Biosynthetic Pathway ◽  
Carbohydrate Polymer ◽  
Rate Limiting ◽  
Proliferation In Vitro

Rewired metabolism is a hallmark of pancreatic ductal adenocarcinomas (PDA). Previously, we demonstrated that PDA cells enhance glycosylation precursor biogenesis through the hexosamine biosynthetic pathway (HBP) via activation of the rate limiting enzyme, glutamine-fructose 6-phosphate amidotransferase 1 (GFAT1). Here, we genetically ablated GFAT1 in human PDA cell lines, which completely blocked proliferation in vitro and led to cell death. In contrast, GFAT1 knockout did not preclude the growth of human tumor xenografts in mice, suggesting that cancer cells can maintain fidelity of glycosylation precursor pools by scavenging nutrients from the tumor microenvironment. We found that hyaluronic acid (HA), an abundant carbohydrate polymer in pancreatic tumors composed of repeating N-acetyl-glucosamine (GlcNAc) and glucuronic acid sugars, can bypass GFAT1 to refuel the HBP via the GlcNAc salvage pathway. Together, these data show HA can serve as a nutrient fueling PDA metabolism beyond its previously appreciated structural and signaling roles.

Abstract 261: Robust Cardioprotection Afforded by a Previously Unrecognized Link between the Unfolded Protein Response and the Hexosamine Biosynthetic Pathway

2014 ◽  
Vol 115 (suppl_1) ◽  
Author(s):  
Zhao V Wang ◽  
Yingfeng Deng ◽  
Ningguo Gao ◽  
Zully Pedrozo ◽  
Dan Li ◽  
...  
Keyword(s):  
Unfolded Protein Response ◽  
Biosynthetic Pathway ◽  
Ischemia Reperfusion ◽  
Uridine Diphosphate ◽  
Hexosamine Biosynthetic Pathway ◽  
Unfolded Protein ◽  
The Unfolded Protein Response ◽  
Protein Response ◽  
Rate Limiting

Background: The hexosamine biosynthetic pathway (HBP) generates UDP-GlcNAc (uridine diphosphate N-acetylglucosamine) for glycan synthesis and O-linked GlcNAc (O-GlcNAc) protein modifications. Despite the established role of the HBP in glucose metabolism and multiple diseases, regulation of the HBP remains largely undefined. Methods & Results: Here, we show that spliced Xbp1 (Xbp1s), the most conserved signal transducer of the unfolded protein response (UPR), is a direct transcriptional activator of the HBP. We demonstrate that the UPR triggers activation of the HBP by means of Xbp1s-dependent transcription of genes coding for key, rate-limiting enzymes. We establish that this previously unrecognized UPR-HBP axis is triggered in a variety of stress conditions known to promote O-GlcNAc modification. We go on to demonstrate that Xbp1s, acutely stimulated by ischemia/reperfusion (I/R) in heart, confers robust cardioprotection against I/R injury. We also show that HBP induction is required for this cardioprotective response. Mechanistically, HBP may mediate the adaptive branch of the UPR by activating autophagy and ER-associated degradation. Conclusion: These studies reveal that Xbp1s couples the UPR to the HBP, promoting robust cardioprotection during I/R.

scholarly journals Conversion of 5-aminolaevulinate into haem by liver homogenates. Comparison of rat and chick embryo

1981 ◽  
Vol 198 (3) ◽  
pp. 595-604 ◽  
Author(s):  
J F Healey ◽  
H L Bonkowsky ◽  
P R Sinclair ◽  
J F Sinclair
Keyword(s):  
Chick Embryo ◽  
Rat Liver ◽  
Biosynthetic Pathway ◽  
Frozen Storage ◽  
Relevant Information ◽  
Porphobilinogen Deaminase ◽  
Embryo Liver ◽  
Liver Homogenates ◽  
Rate Limiting ◽  
Kinetics Of

1. We have studied the kinetics of the conversion of 5-aminolaevulinate into haem and haem precursors in homogenates of livers of rats and chick embryos. Homogenates of fresh liver from both species efficiently convert 5-aminolaevulinate into haem. After frozen storage for 1 year, homogenates of rat, but not chick, liver have decreased rates of formation of haem with accumulation of more protoporphyrin. The rate of haem formation after storage is restored by addition of Fe2+ and menadione. 2. At all initial concentrations of 5-aminolaevulinate tested (2 microM-1 mM), homogenates of rat liver accumulate less protoporphyrin than haem. In contrast, homogenates of chick embryo liver accumulate more protoporphyrin than haem at concentration of 5-aminolaevulinate greater than 10 microM. Conversion of protoporphyrin into haem by homogenates of fresh or frozen chick embryo liver is not increased by addition of Fe2+. 3. Homogenates of liver from both species accumulate porphobilinogen; the kinetic parameters for this process reflect those of 5-aminolaevulinate dehydratase. 4. The results show that the rate-limiting enzyme for the hepatic conversion of 5-aminolaevulinate into protoporphyrin is porphobilinogen deaminase. In addition, chick liver, compared with rat liver, has only about one-fifth the activity of ferrochelatase, the final enzyme of the haem biosynthetic pathway, which inserts Fe2+ into protoporphyrin to form haem. 5. Comparison of these results with previous studies indicates that the homogenate system described here provides physiologically and clinically relevant information for study of hepatic haem synthesis and its control.

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