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

The glucose-producing amylolytic activity in pancreatic islet tissue was characterized with regard to its properties with glycogen (amyloglucosidase) and maltose (maltase) as substrate, its optimum activity in islets from different strains of mice (NMRI, CBA and C-57BL) and after fasting, and its relation to the insulin secretory response after different secretagogues in vivo. Additionally the effects and fate of injected fungal acid amyloglucosidase were assessed. In the pancreatic islets of NMRI mice both the glycogen-splitting activity and the maltose-splitting activity displayed latency and an acid pH-optimum of about 5.0. After differential centrifugation a significant part of amyloglucosidase activity was found to be confined to the mitochondrial-lysosomal fraction. In crude islet homogenate the apparent Km for maltose at pH 5.0 was 2.1 mM. No Km for glycogen could be given because of complex kinetics in the presence of this substrate. The maltase activity was about 30% lower than the amyloglucosidase activity in islet tissue from NMRI mice. The reverse pattern was observed in the liver. Moreover, the liver amyloglucosidase activity was only one fourth of that of the islet tissue. The amyloglucosidase but not the maltase activity in islet tissue from CBA mice was lower than in islets from NMRI mice. Both activities were very low in islets from C-57 mice. A 24 hr fasting period reduced the amyloglucosidase but not the maltase activity in islets from NMRI mice. The insulin secretory response in vivo to an i.v. arginine load in the different strains and after fasting displayed the same pattern as the islet amyloglucosidase activity, whereas the insulin response following a glucagon injection was largest in the C-57 strain and unaffected by the fasting state. Pretreatment of mice with 0.05 mumol/kg of highly purified fungal amyloglucosidase, moderately (about 35%) enhanced the insulin secretory response to arginine, did not affect the response to glucagon, and greatly (about 100%) enhanced the response to glucose and tolbutamide. Moreover, treatment of mice with lysosomal stabilizers (glucocorticoids) reduced the insulin response to sulphonylureas and glucose, had no effect on the insulin response to beta-adrenergic and cholinergic stimulation, and increased ACTH-induced insulin release. A lysosomal labilizer (progesterone) enhanced the insulin response induced by glucose and tolbutamide.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Islet amyloglucosidase activity: some characteristics, and its relation to insulin secretion stimulated by various secretagogues. 308 68

The development of hydrolase activity in the intestinal brush border membrane is important for the maturation of digestive function in early life. The development and glucocorticoid control of intestinal enzymes were investigated in the mink (Mustela vison), a carnivorous species, in which the intestine matures relatively late in postnatal life. Mink kits (n = 110 from 20 litters) were either not treated or injected intramuscularly for 7 d with saline, adrenocorticotropic hormone [ACTH, 50 micrograms/(kg.d)] or cortisol 21-acetate [synthetic glucocorticoid, 50 mg/(kg.d)]. The kits were killed at 2, 4, 6, 8 or 10 wk of age and the proximal, middle and distal intestine removed for analyses. Lactase activity was maximal at 4 wk and decreased to about 5% of this level during the following 2 wk. Cortisol treatment stimulated total lactase activity at 2 wk (170% that of controls, P < 0.05) and reduced this activity at 4 wk (20% that of controls, P < 0.001). Aminopeptidases N and A underwent their major developmental increases in activity at 4-6 wk and again, enzyme development was stimulated by cortisol. Other enzymes showed either a gradual increase (maltase), a slight decrease (dipeptidylpeptidase IV) or no consistent change (sucrase) in activity with advancing age from 2 to 10 wk, but the activities remained highest in cortisol-treated kits. Treatment with ACTH enhanced the activity of all enzymes at 2 wk but had little effect thereafter. Intestinal hydrolases develop later in the mink and are sensitive to glucocorticoid induction for a longer period in postnatal life than in species such as rats, pigs or humans. The mink is a useful model in studies of the regulatory mechanisms which influence the development of intestinal brush border hydrolases.
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PMID:Intestinal hydrolytic activity in young mink (Mustela vison) develops slowly postnatally and exhibits late sensitivity to glucocorticoids. 881 92