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Incorporation of labelled glycine into reduced glutathione of intact human erythrocytes by enzyme-catalysed exchange. A nuclear-magnetic-resonance study.

ABSTRACT: 1H, 2H and 15N n.m.r. spectroscopy was used to monitor the incorporation of free glycine into the glycine residue of reduced glutathione (GSH) in suspensions of intact human erythrocytes. The following results were obtained. (i) By using 1H spin-echo n.m.r. the exchange reaction between [2H5]glycine and the protonated glycine residue of GSH was studied at various [2H5]glycine concentrations, thus enabling the calculation of an apparent Michaelis constant (Km) and maximal velocity (Vmax.) for the process. (ii) The reaction is catalysed by glutathione synthetase and proceeds most rapidly in the absence of glucose, which is the main physiological energy source of the erythrocyte. (iii) 15N n.m.r. spectroscopy, with a one-pulse sequence, and 2H n.m.r. spectroscopy, with an inversion recovery method, enabled demonstration of the incorporation of labelled glycine into an intra-erythrocyte peptide, consistent with incorporation into GSH. (iv) The exchange reaction, although inhibited by glucose, appeared not to be dependent on low ATP or 2,3-bisphosphoglycerate concentrations.

SUBMITTER: York MJ

PROVIDER: S-EPMC1153824 | biostudies-other | 1982 Oct

REPOSITORIES: biostudies-other

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Project description:Lower circulating levels of glycine are consistently reported in association with cardiovascular disease (CVD), but the causative role and therapeutic potential of glycine in atherosclerosis, the underlying cause of most CVDs, remain to be established. Here, following the identification of reduced circulating glycine in patients with significant coronary artery disease (sCAD), we investigated a causative role of glycine in atherosclerosis by modulating glycine availability in atheroprone mice. We further evaluated the atheroprotective potential of DT-109, a recently identified glycine-based compound with dual lipid/glucose-lowering properties. Glycine deficiency enhanced, while glycine supplementation attenuated, atherosclerosis development in apolipoprotein E-deficient (Apoe-/-) mice. DT-109 treatment showed the most significant atheroprotective effects and lowered atherosclerosis in the whole aortic tree and aortic sinus concomitant with reduced superoxide. In Apoe-/- mice with established atherosclerosis, DT-109 treatment significantly reduced atherosclerosis and aortic superoxide independent of lipid-lowering effects. Targeted metabolomics and kinetics studies revealed that DT-109 induces glutathione formation in mononuclear cells. In bone marrow-derived macrophages (BMDMs), glycine and DT-109 attenuated superoxide formation induced by glycine deficiency. This was abolished in BMDMs from glutamate-cysteine ligase modifier subunit-deficient (Gclm-/-) mice in which glutathione biosynthesis is impaired. Metabolic flux and carbon tracing experiments revealed that glycine deficiency inhibits glutathione formation in BMDMs while glycine-based treatment induces de novo glutathione biosynthesis. Through a combination of studies in patients with CAD, in vivo studies using atherosclerotic mice and in vitro studies using macrophages, we demonstrated a causative role of glycine in atherosclerosis and identified glycine-based treatment as an approach to mitigate atherosclerosis through antioxidant effects mediated by induction of glutathione biosynthesis.

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Incorporation of labelled glycine into reduced glutathione of intact human erythrocytes by enzyme-catalysed exchange. A nuclear-magnetic-resonance study.

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