Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.20 (alpha-glucosidase)
 4,237 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Honeybee alpha-glucosidase I was inactivated with diethylpyrocarbonate (DEPC). The inactivation followed pseudo-first-order kinetics. The rate of the loss of activity was decreased by the addition of a substrate, maltose. Since there was no spectral change in the tyrosine absorption region, it was recognized that DEPC did not react with this residue. The alpha-glucosidase had one free sulfhydryl group, which was not involved in the catalytic reaction, and was not modified by DEPC. On the other hand, the specific reaction of DEPC with a histidyl residue was spectrophotometrically confirmed by an increase in absorption near 240 nm, and the activity of the inactivated enzyme was restored by hydroxylamine. The modification rate of one histidyl residue by DEPC was almost equal to the rate of the activity loss. These results indicate that there is one histidyl residue at or near the catalytic site, and that honeybee alpha-glucosidase I has a single active site.
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PMID:Evidence for a single catalytic site of honeybee alpha-glucosidase I by chemical modification with diethylpyrocarbonate. 142 1

The mechanism of nutrient-evoked insulin release is clearly complex. One part of that mechanism is postulated to be the activation of the glycogenolytic enzyme acid glucan-1,4-alpha-glucosidase. As nitric oxide (NO) has been found to be a potent inhibitor of glucose-stimulated insulin secretion, we have now investigated a possible influence of exogenous NO and inhibition of endogenous NO production on islet acid glucan-1,4-alpha-glucosidase activity in relation to insulin release stimulated by glucose and l-arginine. In isolated islets, NO derived from the intracellular NO donor hydroxylamine inhibited the activation of acid glucan-1, 4-alpha-glucosidase and its isoform acid alpha-glucosidase in parallel with inhibition of glucose-stimulated insulin release. In comparison, other lysosomal enzymes were largely unaffected. Similarly, the spontaneous NO donor sodium nitroprusside, as well as NO gas, when added to islet homogenates, suppressed the activities of these acid alpha-glucosidehydrolases and, to a lesser extent, the activities of other lysosomal enzymes. Finally, in the presence of the NO synthase inhibitor N(G)-nitro-l-arginine methyl ester, insulin release from isolated islets stimulated by glucose or l-arginine was markedly potentiated in parallel with an accompanying increase in the activities of acid glucan-1,4-alpha-glucosidase and acid alpha-glucosidase. Other lysosomal enzymes and neutral alpha-glucosidase were not influenced. We propose that an important inhibitory effect of NO on the insulin secretory processes stimulated by glucose and l-arginine is exerted via inactivation of islet acid glucan-1,4-alpha-glucosidase, a putative key enzyme in nutrient-stimulated insulin release.
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PMID:Nitric oxide, islet acid glucan-1,4-alpha-glucosidase activity and nutrient-stimulated insulin secretion. 1081 Feb 93