In:
Zeitschrift für Naturforschung C, Walter de Gruyter GmbH, Vol. 40, No. 1-2 ( 1985-2-1), p. 29-33
Abstract:
When γ-glutamyltranspeptidase activity in tobacco cells was measured using the artificial substrate γ-glutamyl-p-nitroanilide, liberation of p-nitroaniline was not reduced, but stimulated by addition of glutathione. Therefore, glutathione was not acting as a donator, but as an acceptor of γ-glutamyl moieties in the assay mixture, suggesting that γ-glutamvltranspeptidase is not participating in degradation of glutathione. Feeding experiments with [ 35 S-cys]glutathione supported this conclusion. When tobacco cells were supplied with this peptide as sole sulfur source, glutathione and γ-glutamylcysteine were the only labelled compounds found inside the cells. The low rate of uptake of glutathione apparently prevented the accumulation of measurable amounts of radioactivity in the cysteine pool. A γ-glutamylcyclotransferase, responsible for the conversion of γ-glutamylcysteine to 5-oxo-proline and cysteine was found in ammonium sulfate precipitates of tobacco cell homogenates. The enzyme showed high activities with γ-glutamylmethionine and γ-glutamylcysteine, but not with other γ-glutamyldipeptides or glutathione. From these and previously published experiments [(Rennenberg et a!., Z. Naturforsch. 35c, 708-711 (1980)] , it is concluded that glutathione is degraded in tobacco cells via the following pathway: γ-glu-cys-gly → γ-glu-cys → 5-oxo-proline → glu.
Type of Medium:
Online Resource
ISSN:
1865-7125
,
0939-5075
DOI:
10.1515/znc-1985-1-208
Language:
English
Publisher:
Walter de Gruyter GmbH
Publication Date:
1985
detail.hit.zdb_id:
2078107-6
SSG:
12
