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Renal Drug-Metabolizing Enzymes in Experimental Animals and Humans
Published in Robin S. Goldstein, Mechanisms of Injury in Renal Disease and Toxicity, 2020
GSH conjugation generally functions as a detoxification pathway. However, compounds may undergo bioactivation following GSH conjugation. Recent studies have described enzymes that metabolize S-cysteine conjugates via transamination and β elimination. This work has demonstrated the role of metabolism in the nephrotoxicity of some S-cysteine conjugates. Both deamination and β elimination are catalyzed by pyridoxal phosphate-dependent enzymes. The balance between β elimination and/or deamination depends on the properties of the enzyme and/or the chemical properties of the substrate. Both reactions are possible with a single substrate and with one enzyme. Deamination of amino acids by transamination involves the transfer of an amino group from a donor amino acid to an acceptor a-keto acid and subsequent decarboxylation. Glutamine transaminase K from rat kidney has been shown to catalyze the transamination of S-cysteine conjugates with a-keto-γ-methiolbutyrate (Stevens et al., 1986). Transamination of cysteine conjugates with other α-keto acids and by other enzymes has also been reported; for example, a flavin-dependant amino acid oxidase from rat kidney catalyzes the oxidative deamination of some S-cysteine conjugates with the concomitant reduction of molecular oxygen to hydrogen peroxide (Hamilton, 1985).
Functions of the Liver
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
The liver has an important role in protein catabolism. The rate of protein turnover in the liver is 10 days, which contrasts sharply with the rate of 180 days for muscle proteins. Amino acid degradation is by transamination, deamination and decarboxylation. Oxidative deamination breaks down surplus amino acids and releases energy. Deamination may be coupled with the transfer of an amino group from one amino acid to another (transamination). These reactions produce acetyl CoA, oxoglutarate, succinyl CoA, oxaloacetate and fumarate, all of which enter the citric acid cycle. Amino acids (such as arginine, histidine, lysine, methionine, threonine, phenylalanine and tryptophan) are degraded mainly in the liver, whereas aspartic acid, glutamic acid, glycine, proline and alanine are metabolized in both hepatic and muscle tissue.
Concept of Nutrition
Published in Anil Gupta, Biochemical Parameters and the Nutritional Status of Children, 2020
The surplus amino acids are in the phase of catabolism. These are subjected to a biochemical process of transamination wherein the surplus amino acid is converted into alpha keto acid that enters the TCA cycle and is utilized for production of energy. The excess amino acid also undergoes deamination, through which it is converted into alpha keto acid with the release of ammonia. It is transported to the liver where it is converted into urea that enters blood circulation and is excreted by kidneys.
Dexamethasone increases renal free fatty acids and xanthine oxidase activity in female rats: could there be any gestational impact?
Published in Drug and Chemical Toxicology, 2022
Olufunto O. Badmus, Isaiah W. Sabinari, Lawrence A. Olatunji
Gamma-glutamyl transferase (GGT) was measured by a standardized enzymatic colorimetric method using assay kit obtained from Fortress Diagnostics Limited, Antrim, UK. The GGT in the sample recognized L-γ-Glutamyl-pNA as a specific substrate leading to proportional color development (Braun et al.1978). Alanine transaminase (ALT) was measured by a standardized enzymatic colorimetric method using an assay kit (Catalog Number: BXC0213; Fortress Diagnostics Limited, Antrim, UK). Using this kit, ALT catalyzes the transfer of an amino group from alanine to α-ketoglutarate, the products of this reversible transamination reaction being pyruvate and glutamate. The pyruvate was detected in a reaction that concomitantly converts a nearly colorless probe to color. Also, aspartate aminotransferase (AST) was measured by a standardized enzymatic colorimetric method using an assay kit (Catalog Number: BXC0203; Fortress Diagnostics Limited, Antrim, UK). Using this method, an amino group was transferred from aspartate to α-ketoglutarate. The products of this reversible transamination reaction were oxaloacetate and glutamate. The glutamate was detected in a reaction that concomitantly converts a nearly colorless probe to color. Likewise, alkaline phosphatase (ALP) was measured by standardized enzymatic colorimetric method using an assay kit (Catalog Number: BXC0183; Fortress Diagnostics Limited, Antrim, UK). This method used p-nitrophenyl phosphate (pNPP) as a phosphatase substrate which turns yellow (ODmax= 405 nm) when dephosphorylated by ALP.
Genome-wide association studies of stress score in a Korean Cohort
Published in Stress, 2021
Two SNPs were identified for ActST. The first significant SNP (SNP_A-1897172) is located in locus 171221400 on chromosome 4, in the alpha-aminoadipate aminotransferase (AADAT) gene. The gene undertakes two transaminase activities—the transamination of alpha-aminoadipic acid (a final step in the saccaropine pathway, which is the major pathway for L-lysine catabolism) and the transamination of kynurenine to produce kynurenine acid (the precursor of kynurenic acid which has neuroprotective properties) (Gaudet et al., 2011). Such neurodefensive properties are likely responsible for its relevance to stress. The second SNP in ActST (rs17338026) is found on the metaxin 2 (MTX2) gene, which interacts with mitochondrial membrane proteins and is considered to be important for proteins within the mitochondria (Pastor, 1966).
Bio-efficacy and physiological effects of Eucalyptus globulus and Allium sativum essential oils against Ephestia kuehniella Zeller (Lepidoptera: Pyralidae)
Published in Toxin Reviews, 2020
Morteza Shahriari, Arash Zibaee, Leila Shamakhi, Najmeh Sahebzadeh, Diana Naseri, Hassan Hoda
Amino acids are one of the important molecules which are involved in energy providing, vitellogenin, osmotic contribution, neurotransmission, and cuticle sclerotization of insects (Klowden 2012). Although insects gain essential amino acids directly from ingested food but non-essential ones can be provided through a biochemical processes called tranamination (Nation 2008, Klowden 2012). In transamination, ALT and AST are the key enzymes by converting alanine, aspartate and α-ketoglutarate to oxaloacetate and glutamate (Ramzi et al. 2014). γ-Glutamyl transferase plays a crucial role in synthesis or degradation of glutathione and xenobiotic compounds entered into insects tissues trough γ-glutamyl cycle (Tate and Meister 1985, Ramzi et al. 2014). In the present study, activities of these aminotransferases increased in the treated larvae of E. kuehniella by EOs compared to control larvae. The higher activities of transaminases may imply on protein demands for tissue repair or energy following destructive effects of EOs as well as detoxifying role of γ-GT to protect tissues from further damages. Our findings have already observed by earlier studies (Adel et al. 2010, Mojarab-Mahboubkar and Jalali Sendi 2016, Shahriari and Sahebzadeh 2017).