The hexose-ATP-kinase of wild-type (CBS 819) is, like hexokinase PII of , associated with carbon catabolite repression and phosphorylates D-glucose and D-fructose. The kinase of repression-resistant (Dog) mutants phosphorylates D-glucose, but not D-fructose. Subjecting the wild-type enzyme to 45 °C for a few minutes appears to alter its activity, specificity and kinetic characteristics to that of the mutant enzyme. Fast protein liquid chromatography, with anion-exchange or gel-filtration columns, gel-electrophoresis, and DNA hybridization with the mutant of the (hexokinase PII) gene of , all failed to resolve more than one hexose-ATP-kinase in Hence appears to have a single hexose-ATP-kinase, ∼ 72000, with two catalytic sites, analogous to the aspartate kinase/homoserine dehydrogenase of One site is hexokinase-like and associated with catabolite repression and the other is glucokinase-like. Values for apparent were 7.2 mM-D-fructose and 0.55 mM-D-glucose (‘hexokinase’ site) and 0.078 mM-D-glucose (‘glucokinase’ site).


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