Stereospecific d-Glucokinase of Aerobacter aerogenes

A constitutive stereospecific d-glucokinase was purified over 1000-fold from extracts of Aerobacter aerogenes PRL-R3. Only d-glucose (Km = 8 x 10-5 m and d-glucosamine (Ki = 4 x 10-4 m) were phosphorylated. The enzyme was inhibited by d-xylose (competitive with d-glucose, Ki = 3 x 10-3 m) but not by 34 other sugars and related compounds tested. It was inhibited by adenosine diphosphate (competitive with adenosine triphosphate, Ki = 4 x 10-4 m) but not by d-glucose 6-phosphate or d-mannose 6-phosphate. The pH optimum was 7.5 in glycylglycine buffer and about 8.9 in glycine buffer. Other properties studied were phosphoryl donor specificity, metal ion specificity, sedimentation coefficient, and stability. The product of d-glucose phosphorylation was identified as d-glucose 6-phosphate.