scholarly journals Increased activity of renal glycine-cleavage-enzyme complex in metabolic acidosis

1985 ◽  
Vol 231 (2) ◽  
pp. 477-480 ◽  
Author(s):  
M Lowry ◽  
D E Hall ◽  
J T Brosnan
Keyword(s):  
Metabolic Acidosis ◽  
Serine Hydroxymethyltransferase ◽  
Enzyme Complex ◽  
Glycine Metabolism ◽  
Methylenetetrahydrofolate Dehydrogenase ◽  
Cleavage Enzyme ◽  
Combined Actions ◽  
Glycine Cleavage ◽  
Increased Activity

Glycine is metabolized in isolated renal cortical tubules to stochiometric qualities of ammonia, CO2 and serine by the combined actions of the glycine-cleavage-enzyme complex and serine hydroxymethyltransferase. The rate of renal glycine metabolism by this route is increased in tubules from acidotic rats, but is not affected in vitro by decreasing the incubation pH from 7.4 to 7.1. Metabolic acidosis caused an increase in the renal activity of the glycine-cleavage-enzyme complex, but there were no changes in the activity of serine hydroxymethyltransferase or of methylenetetrahydrofolate dehydrogenase. This enzymic adaptation permits increased ammoniagenesis from glycine during acidosis. The physiological implications are discussed.

The 1986 Borden Award Lecture. The role of the kidney in amino acid metabolism and nutrition

1987 ◽  
Vol 65 (12) ◽  
pp. 2355-2362 ◽  
Author(s):  
John T. Brosnan
Keyword(s):  
Proximal Tubule ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Acid Metabolism ◽  
Rat Kidney ◽  
High Protein Diet ◽  
Serine Hydroxymethyltransferase ◽  
Glutamine Metabolism ◽  
Cleavage Enzyme ◽  
Glycine Cleavage

Measurement of the arteriovenous differences for free amino acids across rat kidney reveals that glycine and citrulline are removed and serine and arginine are added to the circulation. In addition, glutamine is taken up in large quantities by kidneys of animals that need to excrete large quantities of acid (e.g., diabetic animals, NH4Cl-fed animals, and animals fed a high protein diet). Glutamine is the major precursor of urinary ammonia and thus renal glutamine metabolism plays a key role in acid–base homeostasis. This process occurs primarily in the cells of the convoluted proximal tubule. Glutamine carbon is converted to glucose in acidotic rats and is totally oxidized in dogs. Regulation of glutamine metabolism occurs at two levels: acute regulation and chronic regulation. Acute regulation is, in part, mediated through a fall in intracellular [H+]. This activates α-ketoglutarate dehydrogenase and, ultimately, glutaminase. Chronic regulation involves induction of key enzymes, including, in the rat, glutaminase, glutamate dehydrogenase, and phosphoenolpyruvate carboxykinase. During the acidosis of prolonged starvation, the kidneys' requirement for glutamine must be met from muscle proteolysis and thus becomes a drain on lean body mass. Serine synthesis occurs by two separate pathways: from glycine by the combined actions of the glycine cleavage enzyme and serine hydroxymethyltransferase and from gluconeogenic precursors using the phosphorylated-intermediate pathway. Both pathways are located in the cells of the proximal tubule. Conversion of glycine to serine is ammoniagenic and the activity of the glycine cleavage enzyme is increased in acidosis. The function of serine synthesis by the phosphorylated-intermediate pathway is not apparent. Renal serine synthesis is quantitatively important; in man it is comparable to the serine obtained in the diet. Nevertheless, renal serine synthesis was not sensitive to serine status in rats as neither removal of dietary serine nor supplementation of the diet with serine affected renal serine synthesis. Arginine synthesis occurs from citrulline removed from the circulation. The citrulline is produced in the intestine. The kidney is the major endogenous source of arginine.

scholarly journals Interaction between glycine decarboxylase, serine hydroxymethyltransferase and tetrahydrofolate polyglutamates in pea leaf mitochondria

1994 ◽  
Vol 302 (1) ◽  
pp. 223-228 ◽  
Author(s):  
F Rebeille ◽  
M Neuburger ◽  
R Douce
Keyword(s):  
Dissociation Constants ◽  
Oxidative Degradation ◽  
Maximal Activity ◽  
Serine Hydroxymethyltransferase ◽  
In Vitro Experiments ◽  
Glycine Cleavage System ◽  
Kd Values ◽  
Bulk Medium ◽  
Glycine Cleavage

The aim of the present work was to further determine how the T-protein of the glycine-cleavage system and serine hydroxy-methyltransferase (SHMT), two folate-dependent enzymes from pea leaf mitochondria, interact through a common pool of tetrahydrofolate polyglutamates (H4PteGlun). It was observed that the binding affinity of tetrahydrofolate polyglutamates for these proteins continuously increased with increasing number of glutamates up to six residues. It was also established that, once bound to the proteins, tetrahydrofolate, a very O2-sensitive molecule, was protected from oxidative degradation. The dissociation constants (Kd) of H4PteGlu5, the most predominant form of polyglutamate in the mitochondria, were approximately 0.5 microM for both T-protein and SHMT, whereas the Kd values of CH2-H4PteGlu5 were higher, 2.7 and 7 microM respectively. In a matrix extract from pea leaf mitochondria, the maximal activity of the glycine-cleavage system was about 2.5 times higher than the maximal activity of SHMT. This resulted in a permanent disequilibrium of the SHMT-catalysed reaction which was therefore driven toward the production of serine and H4PteGlun, the thermodynamically unfavourable direction. Indeed, measurements of the steady-state ratio of CH2-H4PteGlun/H4PteGlun (n = 1 or n = 5) during the course of glycine oxidation demonstrated that the methylene form accounted for 65-80% of the folate pool. This indicates that, in our in vitro experiments, CH2-H4PteGlun with long polyglutamate chains accumulated in the bulk medium. This observation suggests that, in these in vitro experiments at least, there was no channelling of CH2-H4PteGlu5 between the T-protein and SHMT.

Serine synthesis in rat kidney: studies with perfused kidney and cortical tubules

1986 ◽  
Vol 250 (4) ◽  
pp. F649-F658
Author(s):  
M. Lowry ◽  
D. E. Hall ◽  
J. T. Brosnan
Keyword(s):  
Proximal Tubule ◽  
Rat Kidney ◽  
Distal Tubule ◽  
Serine Hydroxymethyltransferase ◽  
Percoll Gradient ◽  
Tight Coupling ◽  
Cleavage Enzyme ◽  
14Co2 Production ◽  
Glycine Cleavage ◽  
Perfused Kidney

Renal serine synthesis was studied in the isolated perfused kidney and in isolated cortical tubules. Serine was produced by the perfused kidney from both glycine and aspartate, indicating flux through at least two separate pathways: serine hydroxymethyltransferase and either the nonphosphorylated or phosphorylated intermediate pathways. The precise nephron site of serine production was determined by measuring serine synthesis from various precursors and the activities of enzymes of both pathways in isolated tubules fractionated on a Percoll gradient into proximal tubule and distal tubule fractions. Both pathways of serine synthesis were located in proximal tubules. Detailed studies of serine synthesis from glycine demonstrated extremely tight coupling between the glycine cleavage enzyme and serine hydroxymethyltransferase, since the rate of 14CO2 production from [2-14C]glycine was less than 5% of that of [1-14C]glycine, whereas the rate of incorporation of 14C into serine from [2-14C]glycine was double that from [1-14C]glycine. These studies demonstrate that the kidney can synthesize serine by two separate pathways, both located in the cells of the proximal tubule.

AnEscherichia coliprotein with homology to the H-protein of the glycine cleavage enzyme complex from pea and chicken liver

DNA Sequence ◽  
1991 ◽  
Vol 2 (1) ◽  
pp. 13-17 ◽  
Author(s):  
Lorraine T. Stauffer ◽  
Paula S. Steiert ◽  
John G. Steiert ◽  
George V. Stauffer
Keyword(s):  
Chicken Liver ◽  
Enzyme Complex ◽  
Cleavage Enzyme ◽  
Glycine Cleavage ◽  
H Protein

Glycine cleavage enzyme complex: Molecular cloning and expression of the H-protein cDNA from cultured human skin fibroblasts

2011 ◽  
Vol 89 (3) ◽  
pp. 299-307 ◽  
Author(s):  
Agnes Zay ◽  
Francis Y.M. Choy ◽  
Chelsea Patrick ◽  
Graham Sinclair
Keyword(s):  
Pichia Pastoris ◽  
Human Skin ◽  
Lipoic Acid ◽  
Culture Medium ◽  
Skin Fibroblasts ◽  
Enzyme Complex ◽  
Human Skin Fibroblasts ◽  
Cleavage Enzyme ◽  
Glycine Cleavage ◽  
H Protein

The human H-protein is one of four essential components (H-, L-, P-, and T-proteins) of the mammalian glycine cleavage enzyme complex and its function is involved in the pathogenesis and diagnosis of glycine encephalopathy. A transcript corresponding to the glycine cleavage H-protein functional gene was isolated from cultured human skin fibroblasts along with a transcript for a putative processed pseudogene on chromosome 2q33.3. Sequence analysis of the fibroblast H-protein functional gene transcript showed complete identity to that reported from human liver. The H-protein cDNA was subsequently cloned with a hexahistidine affinity tag in the Pichia pastoris plasmid vector pPICZαA and recombined into the yeast genome downstream of the alcohol oxidase promoter for methanol-induced expression. The recombinant H-protein was secreted into the culture medium and purified to homogeneity using a one-step nickel-nitrilotriacetic acid resin column. Approximately 4 mg of homogeneous H-protein was obtained from 1 L of culture medium. Since the attachment of a lipoic acid prosthetic group is required for H-protein function, we have expressed and purified E. coli lipoate protein ligase and succeeded in lipoylating H-protein, converting the apo-H-protein to the functional holo-H-protein. A lipoamide dehydrogenase assay was performed to confirm that the apo-H-protein was inactive, whereas the holo-H-protein was approximately 2.3-fold more active than free lipoic acid as a hydrogen donor in driving the reaction. The availability of copious amounts of human recombinant H-protein by using Pichia pastoris expression and affinity purification will facilitate the elucidation of the structure and function of the H-protein and its relationship to the P-, T-, and L-proteins in the glycine cleavage enzyme complex. In view of the fact that there is no detectable glycine cleavage enzyme activity in human skin fibroblasts, we speculate that a plausible function of the H-protein is to interact with the L-protein, which is also part of the l-ketoglutarate dehydrogenase complex present in fibroblasts.

Pharmacophore Modeling and Docking Studies to Investigate Potential Leads for the Development of β -Secretase APP Cleavage Enzyme-1 (BACE-1) Inhibitors

2019 ◽  
Vol 16 (7) ◽  
pp. 775-784
Author(s):  
Richa Arya ◽  
Satya Prakash Gupta ◽  
Sarvesh Paliwal ◽  
Swapnil Sharma ◽  
Kirtika Madan ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Medical Condition ◽  
Pharmacophore Model ◽  
Pharmacophore Modeling ◽  
Docking Studies ◽  
Pyridine Derivative ◽  
Cleavage Enzyme ◽  
Bace 1

Background: Alzheimer’s disease is a medical condition with detrimental brain health. It is majorly diagnosed in aging individuals plaque in β) characterized by accumulated Amyloidal beta (A 1 BACE) 1 secretase APP cleavage enzyme βneurological areas. The ) is the target of choice that can be exploited to find drugs against Alzheimer’s disease. Methods: A series of BACE-1 inhibitors with reported binding constant were considered for the development of a feature based pharmacophore model. Results: The good correlation coefficient (r=0.91) and RMSD of 0.93 was observed with 30 compounds in training set. The model was validated internally (r2test=0.76) as well as externally by Fischer validation. The pharmacophore based virtual screening retrieved compounds that were docked and biologically evaluated. Conclusion: The three structurally diverse molecules were tested by in-vitro method. The pyridine derivative with highest fit value (6.9) exhibited IC50 value of 2.70 µM and thus was found to be the most promising lead molecule as BACE-1 inhibitor.

scholarly journals Ibrexafungerp: A First-in-Class Oral Triterpenoid Glucan Synthase Inhibitor

2021 ◽  
Vol 7 (3) ◽  
pp. 163 ◽  
Author(s):  
Sabelle Jallow ◽  
Nelesh P. Govender
Keyword(s):  
Pathogenic Fungi ◽  
Candida Spp ◽  
Fungal Cell ◽  
Favourable Safety ◽  
Favourable Safety Profile ◽  
Synthase Inhibitor ◽  
Increased Activity ◽  
In Vitro Data

Ibrexafungerp (formerly SCY-078 or MK-3118) is a first-in-class triterpenoid antifungal or “fungerp” that inhibits biosynthesis of β-(1,3)-D-glucan in the fungal cell wall, a mechanism of action similar to that of echinocandins. Distinguishing characteristics of ibrexafungerp include oral bioavailability, a favourable safety profile, few drug–drug interactions, good tissue penetration, increased activity at low pH and activity against multi-drug resistant isolates including C. auris and C. glabrata. In vitro data has demonstrated broad and potent activity against Candida and Aspergillus species. Importantly, ibrexafungerp also has potent activity against azole-resistant isolates, including biofilm-forming Candida spp., and echinocandin-resistant isolates. It also has activity against the asci form of Pneumocystis spp., and other pathogenic fungi including some non-Candida yeasts and non-Aspergillus moulds. In vivo data have shown IBX to be effective for treatment of candidiasis and aspergillosis. Ibrexafungerp is effective for the treatment of acute vulvovaginal candidiasis in completed phase 3 clinical trials.

scholarly journals The loss of SHMT2 mediates 5-fluorouracil chemoresistance in colorectal cancer by upregulating autophagy

Oncogene ◽  
2021 ◽  
Author(s):  
Jian Chen ◽  
Risi Na ◽  
Chao Xiao ◽  
Xiao Wang ◽  
Yupeng Wang ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Patient Survival ◽  
Serine Hydroxymethyltransferase ◽  
First Line ◽  
Xenograft Models ◽  
Potential Opportunity ◽  
First Line Treatment ◽  
Novel Therapeutic

Abstract5-Fluorouracil (5-FU)-based chemotherapy is the first-line treatment for colorectal cancer (CRC) but is hampered by chemoresistance. Despite its impact on patient survival, the mechanism underlying chemoresistance against 5-FU remains poorly understood. Here, we identified serine hydroxymethyltransferase-2 (SHMT2) as a critical regulator of 5-FU chemoresistance in CRC. SHMT2 inhibits autophagy by binding cytosolic p53 instead of metabolism. SHMT2 prevents cytosolic p53 degradation by inhibiting the binding of p53 and HDM2. Under 5-FU treatment, SHMT2 depletion promotes autophagy and inhibits apoptosis. Autophagy inhibitors decrease low SHMT2-induced 5-FU resistance in vitro and in vivo. Finally, the lethality of 5-FU treatment to CRC cells was enhanced by treatment with the autophagy inhibitor chloroquine in patient-derived and CRC cell xenograft models. Taken together, our findings indicate that autophagy induced by low SHMT2 levels mediates 5-FU resistance in CRC. These results reveal the SHMT2–p53 interaction as a novel therapeutic target and provide a potential opportunity to reduce chemoresistance.

scholarly journals Acceleration of cellodextrin phosphorolysis for bioelectricity generation from cellulosic biomass by integrating a synthetic two-enzyme complex into an in vitro synthetic enzymatic biosystem

2019 ◽  
Vol 12 (1) ◽  
Author(s):  
Dongdong Meng ◽  
Ranran Wu ◽  
Juan Wang ◽  
Zhiguang Zhu ◽  
Chun You
Keyword(s):  
Reaction Rate ◽  
Specific Interaction ◽  
Renewable Resource ◽  
Cellulosic Biomass ◽  
Initial Reaction ◽  
Enzyme Complex ◽  
Bioelectricity Generation ◽  
Favorable Reaction ◽  
Enzyme Complexes

Abstract Background Cellulosic biomass, the earth’s most abundant renewable resource, can be used as substrates for biomanufacturing biofuels or biochemicals via in vitro synthetic enzymatic biosystems in which the first step is the enzymatic phosphorolysis of cellodextrin to glucose 1-phosphate (G1P) by cellodextrin phosphorylase (CDP). However, almost all the CDPs prefer cellodextrin synthesis to phosphorolysis, resulting in the low reaction rate of cellodextrin phosphorolysis for biomanufacturing. Results To increase the reaction rate of cellodextrin phosphorolysis, synthetic enzyme complexes containing CDP and phosphoglucomutase (PGM) were constructed to convert G1P to glucose 6-phosphate (G6P) rapidly, which is an important intermediate for biomanufacturing. Four self-assembled synthetic enzyme complexes were constructed with different spatial organizations based on the high-affinity and high-specific interaction between cohesins and dockerins from natural cellulosomes. Thus, the CDP–PGM enzyme complex with the highest enhancement of initial reaction rate was integrated into an in vitro synthetic enzymatic biosystem for generating bioelectricity from cellodextrin. The in vitro biosystem containing the best CDP–PGM enzyme complex exhibited a much higher current density (3.35-fold) and power density (2.14-fold) than its counterpart biosystem containing free CDP and PGM mixture. Conclusions Hereby, we first reported bioelectricity generation from cellulosic biomass via in vitro synthetic enzymatic biosystems. This work provided a strategy of how to link non-energetically favorable reaction (cellodextrin phosphorolysis) and energetically favorable reaction (G1P to G6P) together to circumvent unfavorable reaction equilibrium and shed light on improving the reaction efficiency of in vitro synthetic enzymatic biosystems through the construction of synthetic enzyme complexes.

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