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- Title
Decreased Ca2(+)-ATPase activity after glycosylation of erythrocyte membranes in vivo and in vitro.
- Authors
González Flecha, Francisco L.; Bermúdez, Mónica C.; Cédola, Norberto V.; Gagliardino, Juan J.; Rossi, Juan P. F. C.; González Flecha, F L; Bermúdez, M C; Cédola, N V; Gagliardino, J J; Rossi, J P
- Abstract
Erythrocyte membranes drawn from diabetic patients with poor metabolic control have increased protein glycosylation and decreased Ca2(+)-ATPase activity. A significant relationship was found between these two parameters. Similar results were obtained when protein glycosylation and Ca2(+)-ATPase activity were measured in membranes from normal erythrocytes preincubated with glucose. In this condition, both parameters showed a clear time and dose dependence. Incubation of erythrocyte membranes instead of intact erythrocytes with glucose and glucose-6-phosphate strongly suggests that only the glycosylation of the membrane inner-surface proteins can affect Ca2(+)-ATPase activity. The simultaneous presence of 10 mM glucose and 5 mM ATP in the incubation medium did not affect the degree of erythrocyte membrane protein glycosylation but significantly blocked the inhibitory effect of glucose on Ca2(+)-ATPase activity. However, 5 mM ATP only partially blocked the inhibitory effect of 100 mM glucose, suggesting a competitive mechanism of glucose and ATP for the enzyme active site. Our results show that glycosylation of erythrocyte membrane proteins significantly inhibits Ca2(+)-ATPase activity. This effect could contribute to the development of the capillary closure process observed in diabetic patients. Furthermore, it could represent an index of a general impairment of enzyme function arising in cells chronically exposed to high glucose levels.
- Publication
Diabetes, 1990, Vol 39, Issue 6, p707
- ISSN
0012-1797
- Publication type
journal article
- DOI
10.2337/diabetes.39.6.707