肝脏和胰岛素分泌细胞中己糖激酶和葡萄糖激酶活性的异头特异性。
Anomeric specificity of hexokinase and glucokinase activities in liver and insulin-producing cells.
作者信息
Sener A, Giroix M H, Dufrane S P, Malaisse W J
出版信息
Biochem J. 1985 Sep 1;230(2):345-51. doi: 10.1042/bj2300345.
Conflicting data have been reported concerning the anomeric specificity of glucokinase. In the present study, liver hexokinase (Km for D-glucose 0.4 mM) displayed a higher affinity for but lower Vmax. with alpha- than with beta-D-glucose. The velocity of the reaction catalysed by liver glucokinase was higher with with beta- than with alpha-D-glucose, whatever the glucose concentration. The apparent Km of glucokinase was somewhat lower, however, with alpha- than with beta-D-glucose. Comparable results were obtained for the high-Km glucokinase-like enzymic activity present in normal pancreatic islets or insulin-producing tumoral cells. These results suggest that the anomeric specificity of glucokinase cannot account for the higher rate of glycolysis found in islets exposed to alpha- as distinct from beta-D-glucose.
关于葡萄糖激酶的异头物特异性，已报道了相互矛盾的数据。在本研究中，肝脏己糖激酶（对D-葡萄糖的Km为0.4 mM）对α-D-葡萄糖的亲和力较高，但Vmax较低，而对β-D-葡萄糖的亲和力较低。无论葡萄糖浓度如何，肝脏葡萄糖激酶催化的反应速度对β-D-葡萄糖比对α-D-葡萄糖更高。然而，葡萄糖激酶的表观Km对α-D-葡萄糖比对β-D-葡萄糖略低。对于正常胰岛或产生胰岛素的肿瘤细胞中存在的高Km葡萄糖激酶样酶活性，也获得了类似的结果。这些结果表明，葡萄糖激酶的异头物特异性不能解释在暴露于α-D-葡萄糖而非β-D-葡萄糖的胰岛中发现的较高糖酵解速率。
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