Functional characteristics of hexokinase bound to the type a and type B sites of bovine brain mitochondria. |
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Authors: | Marcelo de Cerqueira Cesar John E Wilson |
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Affiliation: | Departamento de Ciencias Basicas, Universidade de S?o Paulo, 13630-970, Pirassununga, SP, Brazil. |
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Abstract: | Hexokinase is released from Type A sites of brain mitochondria in the presence of glucose 6-phosphate (Glc-6-P); enzyme bound to Type B sites remains bound. Hexokinase of freshly isolated bovine brain mitochondria (Type A:Type B, approximately 40:60) selectively uses intramitochondrial ATP as substrate and is relatively insensitive to the competitive (vs ATP) inhibitor and Glc-6-P analog, 1,5-anhydroglucitol 6-phosphate (1,5-AnG-6-P). After removal of hexokinase bound at Type A sites, the remaining enzyme, bound at Type B sites, does not show selectivity for intramitochondrial ATP and has increased sensitivity to 1,5-AnG-6-P. Thus, the properties of the enzyme bound at Type B sites are modified by removal of hexokinase bound at Type A sites. It is suggested that mechanisms for regulation of mitochondrial hexokinase activity, and thereby cerebral glycolytic metabolism, may depend on the ratio of Type A:Type B sites, which varies in different species. |
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Keywords: | hexokinase, mitochondrially bound hexokinase, brain |
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