Free amino acids of testes. Concentrations of free amino acids in the testes of several species and the precursors of glutamate and glutamine in rat testes in vivo.
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ABSTRACT:
SUBMITTER: Mushahwar IK
PROVIDER: S-EPMC1177598 | biostudies-other | 1973 Mar
REPOSITORIES: biostudies-other
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Project description:High enantiomeric excesses (ee's) of l-amino acids, including non-proteinogenic amino acid isovaline (Iva), were discovered in the Murchison meteorite, but the detailed molecular mechanism responsible for the observed ee of amino acids remains elusive and inconsistent, because Iva has an inverted circular dichroism (CD) spectrum with respect to α-H amino acids, e.g., alanine. To address this issue, we resort to accurate ab initio calculations for amino acids and their precursors in the Strecker synthesis. We evaluated their photolysis-induced ee in the range 5-11 eV including the Lyman alpha emission line (Lyα), the typical intensive 10.2 eV radiation ascribed to the early phase of galactic evolution. We show that only the aminonitrile precursors are characterized by positive ee in the Lyα region, explaining why right-handed circularly polarized Lyα (R-CP-Lyα) induces homologous l-amino acids. This study shows that the homochirality of amino acids is produced at the aminonitrile precursors stage.
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Project description:L-Proline is a multifunctional amino acid that plays an essential role in primary metabolism and physiological functions. Proline is oxidized to glutamate in the mitochondria and the FAD-containing enzyme proline oxidase (PO) catalyzes the first step in L-proline degradation pathway. Alterations in proline metabolism have been described in various human diseases, such as hyperprolinemia type I, velo-cardio-facial syndrome/Di George syndrome, schizophrenia and cancer. In particular, the mutation giving rise to the substitution Leu441Pro was identified in patients suffering of schizophrenia and hyperprolinemia type I. Here, we report on the expression of wild-type and L441P variants of human PO in a U87 glioblastoma human cell line in an attempt to assess their effect on glutamate metabolism. The subcellular localization of the flavoenzyme is not altered in the L441P variant, for which specific activity is halved compared to the wild-type PO. While this decrease in activity is significantly less than that previously proposed, an effect of the substitution on the enzyme stability is also apparent in our studies. At 24 hours of growth from transient transfection, the intracellular level of proline, glutamate, and glutamine is decreased in cells expressing the PO variants as compared to control U87 cells, reaching a similar figure at 72 h. On the other hand, the extracellular levels of the three selected amino acids show a similar time course for all clones. Furthermore, PO overexpression does not modify to a significant extent the expression of GLAST and GLT-1 glutamate transporters. Altogether, these results demonstrate that the proline pathway links cellular proline levels with those of glutamate and glutamine. On this side, PO might play a regulatory role in glutamatergic neurotransmission by affecting the cellular concentration of glutamate.
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Project description:1. The concentrations of alanine, aspartate, glutamate, glutamine and serine plus threonine have been measured by enzymic methods in ;quick-frozen' livers from normal, starved, alloxan-diabetic and phlorrhizin-treated rats. 2. The hepatic concentrations of alanine and serine plus threonine were decreased in rats starved for 48hr. Treatment of these rats with phlorrhizin resulted in a rapid fall (within 2(1/2)hr.) in the concentrations of all the glucogenic amino acids except serine plus threonine, which increased. The pattern for alloxan-diabetic rats was similar to that for phlorrhizin-treated animals, except that here serine plus threonine also decreased in concentration. 3. The effects of anoxia on the hepatic concentrations of the glucogenic amino acids are reported. 4. Inhibition of glutamate-pyruvate transaminase in vivo by l-cycloserine resulted in the accumulation of alanine in situations involving high rates of gluconeogenesis from endogenous amino acids. 5. Measurements of the concentrations of the reactants of the glutamate-pyruvate transaminase and glutamate-oxoglutarate transaminase systems in various metabolic states suggest that they are both at or near equilibrium in rat liver. 6. New enzymic methods are described for the determination of serine plus threonine and alanine.
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Project description:ObjectivesInsulin resistance (IR) in adolescents with obesity is associated with a sex-dependent metabolic 'signature' comprising the branched-chain amino acids (BCAAs), glutamate/glutamine, C3/C5 acylcarnitines and uric acid. Here, we compared the levels of branched-chain α-keto acids (BCKAs) and glutamate/glutamine, which are the byproducts of BCAA catabolism and uric acid among adolescents with obesity prior to and following a 6-month lifestyle-intervention program.MethodsFasting plasma samples from 33 adolescents with obesity (16 males, 17 females, aged 12-18 year) were analysed by flow-injection tandem MS and LC-MS/MS. Multiple linear regression models were used to correlate changes in BCKAs, glutamate/glutamine and uric acid with changes in weight and insulin sensitivity as assessed by HOMA-IR, adiponectin and the ratio of triglyceride (TG) to HDL. In predictive models, BCKAs, glutamate/glutamine and uric acid at baseline were used as explanatory variables.ResultsBaseline BCKAs, glutamate/glutamine and uric acid were higher in males than females despite comparable BMI-metrics. Following lifestyle-intervention, α-keto-β-methylvalerate (α-KMV, a metabolic by product of isoleucine) decreased in males but not in females. The ratio of BCKA/BCAA trended lower in males. In the cohort as a whole, BCKAs correlated positively with the ratio of TG to HDL at baseline and HOMA-IR at 6-month-follow-up. Glutamate/glutamine was positively associated with HOMA-IR at baseline and 6-month-follow-up. A reduction in BCKAs was associated with an increase in adiponectin, and those with higher BCKAs at baseline had higher adiponectin levels at 6-month-follow-up. Interestingly those adolescents with higher uric acid levels at baseline had greater reduction in weight.ConclusionsBCKAs and glutamate/glutamine may serve as biomarkers of IR in adolescents with obesity, and uric acid might serve as a predictor of weight loss in response to lifestyle-intervention. Differential regulation of BCAA catabolism in adolescent males and females implicates critical roles for sex steroids in metabolic homeostasis.
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