Some relations between ascorbic acid and glutathione

Hopkins, Frederick Gowland; Morgan, Edward J.

doi:10.1042/bj0301446

Cited by 146 publications

(35 citation statements)

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“…The experiments of Hopkins & Morgan [1936] on the system ascorbic acid-glutathione-ascorbic acid-oxidase, which Kertesz [1938] was apparently unable to confirm, have been repeated and extended, and the original results completely confirmed. In particular the effect of variations in pH on the enzymic activities of oxidase preparations has been determined.…”

Section: Discussionmentioning

confidence: 99%

“…

Kertesz has since stated [1938] that he was unable to reproduce these experimental results.

…”

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confidence: 99%

“…Hopkins & Morgan [1936] reported a circumstance involving some difficulty in explanation. Though typical protection was obtained in the system when dialysed juice was employed, dialysis nevertheless diminished the power of preparations to promote reduction.…”

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Further observations on the system ascorbic acid-glutathione-ascorbic acid-oxidase

Crook

Hopkins

1938

Biochemical Journal

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IN a paper by Hopkins & Morgan [1936] it was shown that in aqueous solutions containing Szent Gyorgyi's oxidase together with ascorbic acid and glutathione, the former is protected by the latter from oxidation by the enzyme, while the glutathione is itself oxidized vicariously at a rate corresponding to that at which the ascorbic acid is oxidized when alone with the enzyme in similar concentrations. It was also shown that under the influence of similar enzyme preparations the reduction of dehydroascorbic acid by GSH is much faster than the oxidation of ascorbic acid, and also much faster than the reduction when uncatalysed.Kertesz has since stated [1938] that he was unable to reproduce these experimental results. He found that GSH added to solutions of ascorbic acid containing the oxidase had no effect on the oxidation of the ascorbic acid at pH 6. At pH 7 4, while the GSH inhibited to some extent the oxidation of ascorbic acid, both substances were oxidized simultaneously. He found further that the reduction of dehydroascorbic acid by GSH was not catalysed by the enzyme preparation used by him.It became clearly desirable that the experiments should be repeated, and the present paper deals with such repetitions together with some extensions. They have involved the use of many different enzyme preparations, and they show that the results published by Hopkins and Morgan are invariably reproducible. The enzyme preparations used by these authors were all derived from cabbages or from cauliflower florets. Kertesz employed cauliflowers, but also used cucumber juice. With no preparation did he obtain results comparable with those of the earlier workers. In the following sections experiments with cauliflower florets will be first described; certain others obtained with cucumber juice will afterwards receive special reference.Unless an explanation which we will later venture to put forward is justified, we seem to be faced with an inexplicable difference in experimental experience.ExPFiMENTiAT. The cauliflowers employed have been both English-grown and imported.The concentration (or activity) of the oxidase has varied widely in different cases. In general the fresher the source of the supply the greater was the activity of the juice, but it varied apparently with the degree of maturity of the florets. The juice was expressed with avoidance of contact with Fe or Cu, and glassdistilled water was always used for making up solutions. The juice in each case was centrifuged before use, but was not otherwise fractionated. Owing to the wide variations in enzyme concentration we found it desirable to make a preliminary estimation of the rate at which each preparation oxidized a known ( 1356 )

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Section: Discussionmentioning

confidence: 99%

“…

Kertesz has since stated [1938] that he was unable to reproduce these experimental results.

…”

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confidence: 99%

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Further observations on the system ascorbic acid-glutathione-ascorbic acid-oxidase

Crook

Hopkins

1938

Biochemical Journal

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“…Glutathione monoester administration also protects against cellular damage associated with administration of buthionine sulfoximine as discussed below. It has long been thought that the reduction of dehydroascorbate to ascorbate involves reaction with glutathione (36)(37)(38)(39), and recent studies indicate that this reaction is catalyzed by glutaredoxin and protein disulfide isomerase (40). Treatment of newborn rats with buthionine (28).…”

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Biosynthesis and Functions of Glutathione, an Essential Biofactor

Meister

1992

Journal of Nutritional Science and Vitaminology, J Nutr Sci Vit

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“…A number of workers have, however, suggested that ascorbic acid is concerned in the transport of hydrogen in respiratory metabolism, and that the two forms of ascorbic acid constitute an oxidation-reduction couple (Szent-Gyorgyi, 1931;Hopkins & Morgan, 1936;Straschitzki & Rubin, 1936;Crook, 1941;James & Cragg, 1943;James, Heard & James, 1944;Crook & Morgan, 1944;Waygood, 1950). Potato tissue does not appear to contain an enzyme system which can oxidize ascorbic acid directly (Johnson & Zilva, 1937), and the rapid oxidation of ascorbic acid to dehydroascorbic in potato extracts under aerobic conditions was presumed to be due to indirect oxidation by polyphenolase.…”

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confidence: 99%