Anomeric Specificity of Mammalian Hexokinase

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Abstract
The anomeric specificity of hexokinase was examined in crude homogenates of rat parotid gland, erythrocytes and pancreatic islets. At 8.degree. C, the .alpha./.beta. ratio in maximal velocity averaged 0.73, 0.66 and 0.75 in the parotid, erythrocytes and pancreatic islets, respectively. Hexokinase displayed a greater affinity for .alpha.- than .beta.-D-glucose as judged from three criteria: the Km value, the reaction velocity measured with mixtures of the two anomers and their effect upon the phosphorylation of D-[U-14C] glucose in anomeric equilibrium. The latter procedure yielded an .alpha./.beta. ratio in Km close to 0.51, 0.49 and 0.39 in parotid, erythrocytes and pancreatic islets, respectively. Within the limits of this study, the anomeric specificity of mammalian hexokinase would appear to be a mirror image of that of yeast hexokinase.

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