Glutathione Synthesis in Human Erythrocytes

Majerus, Philip W.; Brauner, M. J.; Smith, Michael B.; Minnich, Virginia

doi:10.1172/jci106652

Cited by 50 publications

(14 citation statements)

References 15 publications

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“…Interestingly, synthesis takes place intracellularly, whereas GSH catabolism is exclusively an extracellular event. The first and rate-limiting step of GSH synthesis is the ligation of glutamate to cysteine by the enzyme, γ-glutamyl cysteine synthetase (GCS) (aka glutamate cysteine ligase) (Majerus et al, 1971; Minnich et al, 1971). GCS is a heterodimer of a catalytic (GCLC) and a modulatory (GCLM) subunit, and the expression of these two subunits is driven by Nrf2 (Kwak et al, 2003).…”

Section: Preservation Of Rpe Integrity and Functionmentioning

confidence: 99%

Mechanisms for Countering Oxidative Stress and Damage in Retinal Pigment Epithelium

Plafker¹,

O'Mealey²,

Szweda³

2012

International Review of Cell and Molecular Biology

106

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Clinical and experimental evidence supports that chronic oxidative stress is a primary contributing factor to numerous retinal degenerative diseases, such as age-related macular degeneration (AMD). Eyes obtained postmortem from AMD patients have extensive free radical damage to the proteins, lipids, DNA, and mitochondria of their retinal pigment epithelial (RPE) cells. In addition, several mouse models of chronic oxidative stress develop many of the pathological hallmarks of AMD. However, the extent to which oxidative stress is an etiologic component versus its involvement in disease progression remains a major unanswered question. Further, whether the primary target of oxidative stress and damage is photoreceptors or RPE cells, or both, is still unclear. In this review, we discuss the major functions of RPE cells with an emphasis on the oxidative challenges these cells encounter and the endogenous antioxidant mechanisms employed to neutralize the deleterious effects that such stresses can elicit if left unchecked.

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Section: Preservation Of Rpe Integrity and Functionmentioning

confidence: 99%

Mechanisms for Countering Oxidative Stress and Damage in Retinal Pigment Epithelium

Plafker¹,

O'Mealey²,

Szweda³

2012

International Review of Cell and Molecular Biology

106

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“…y-Glutamylcysteine synthetase which catalyzes this reaction has been purified from rat liver [9], hog liver [lo], rat kidney [Ill, bovine and human erythrocytes [12,13] and bovine lens [14]. Lens y-glutaniylcysteine synthetase is quite specific for L-glutamate, but less specific for the L-cysteine moiety [14,1S].…”

mentioning

confidence: 99%

Bovine Lenticular γ‐Glutamylcysteine Synthetase: Reaction Sequence

Buskirk

Gander

Rathbun

1978

European Journal of Biochemistry

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The sequence of substrate addition and product release during the reaction catalyzed by y-glutamylcysteine synthetase was investigated with purified enzyme from bovine lens. Thermal inactivation and kinetic studies suggest that L-glutamate is the first substrate to bind to the enzyme. L-6-Chloroalanine was used as the L-cysteine analogue. Utilizing substrate activation and product inhibition studies, the following reaction sequence was determined : L-glutamate binding, ATP binding, ADP release, L-P-chloroalanine binding, followed by inorganic phosphate and then dipeptide release. The implications of this mechanism with regard to control of the enzyme in situ and its importance in glutathione synthesis are discussed.

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“…Erythrocyte glutathione exhibits an amino-acid turnover that is relatively slow (several days) as compared, e.g., to that of the liver (5). The enzymes that catalyze the synthesis of glutathione have been found in and purified from erythrocytes (6)(7)(8), but little information is available about the metabolic fate of erythrocyte glutathione. It has been suggested that the observed turnover of glutathione in circulating erythrocytes is due to oxidation of glutathione to the corresponding disulfide followed by active transport of the oxidized form of glutathione out of the erythrocyte (9); thus, according to this interl)retation glutathione is not degraded to its constituent amino acids within the erythrocyte.…”

mentioning

confidence: 99%

Formation of 5-Oxoproline from Glutathione in Erythrocytes by the γ-Glutamyltranspeptidase-Cyclotransferase Pathway

Palekar

Tate

Meister

1974

Proc. Natl. Acad. Sci. U.S.A.

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-y-Glutamyltranspeptidase activity was demonstrated in the membrane fraction of rabbit erythrocytes. The activity observed (with glutathione and various amino-acid acceptors) was similar in magnitude to that of the -y-glutamylcyclotransferase and -y-glutamylcysteine synthetase activities found in the soluble fraction of the cell. No transpeptidase activity was observed with either -y-glutamyl p-nitroanilide or oxidized glutathione in contrast to the rabbit-kidney enzyme for which these compounds and glutathione serve as substrates. Erythrocyte suspensions and hemolysates formed 5-oxoproline (pyroglutamate; pyrrolidone carboxylate); the rate of 5-oxoproline formation from glutathione by hemolysates was increased by addition of methionine. The findings indicate that 5-oxoproline is an end-product of glutathione metabolism in erythrocytes, and that 5-oxoproline passes out of the erythrocyte and is metabolized in other tissues. The observed rate of 5-oxoproline formation is consistent with the conclusion that the -y-glutamyltranspeptidase-cyclotransferase pathway, together with the synthesis of glutathione from glycine, cysteine, and glutamate, account for a large fraction of the observed amino-acid turnover of erythrocyte glutathione.Although mature erythrocytes do not synthesize protein, they are significantly active in the synthesis of the trilel)tide, glutathione. The functions of erythrocyte glutathione are not fully understood, but there is evidence that glutathione plays an important role in erythrocyte metabolism and in the protection of hemoglobin against oxidation (1, 2). Much attention has been given to the reversible oxidation of glutathione, and it has been suggested that glutathione may function in the regulation of the hexose monol)hosp)hate pathway (3,4). Erythrocyte glutathione exhibits an amino-acid turnover that is relatively slow (several days) as compared, e.g., to that of the liver (5). The enzymes that catalyze the synthesis of glutathione have been found in and purified from erythrocytes (6-8), but little information is available about the metabolic fate of erythrocyte glutathione. It has been suggested that the observed turnover of glutathione in circulating erythrocytes is due to oxidation of glutathione to the corresponding disulfide followed by active transport of the oxidized form of glutathione out of the erythrocyte (9); thus, according to this interl)retation glutathione is not degraded to its constituent amino acids within the erythrocyte.In the present work, we have examined the possibility that erythrocyte glutathione is degraded by a pcathway similar to that which takes place in several other cell types, i.e., enzymatic transl)el)tidation of glutathione with amino acids to form y-glutamyl amino acids and cysteinylglycine (10).Cysteinylglycine is split by a peptidase to its constituent amino acids, and y-glutamyl amino acids are converted by the 293 action of 'y-glutamylcyclotransferase (11)(12)(13)(14) to the corresponding amino acids and 5-oxoproline*. Thus, glutathione ...

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Glutathione Synthesis in Human Erythrocytes

Cited by 50 publications

References 15 publications

Mechanisms for Countering Oxidative Stress and Damage in Retinal Pigment Epithelium

Mechanisms for Countering Oxidative Stress and Damage in Retinal Pigment Epithelium

Bovine Lenticular γ‐Glutamylcysteine Synthetase: Reaction Sequence

Formation of 5-Oxoproline from Glutathione in Erythrocytes by the γ-Glutamyltranspeptidase-Cyclotransferase Pathway

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