Purification and properties of hexokinase from the starfish, Asterias amurensis.
Hexokinase from pyloric caeca of the starfish, Asterias amurensis, was purified to a specific activity of 148 units/mg protein. The purified enzyme appeared to be homogeneous on SDS-polyacrylamide gel electrophoresis. The molecular weight determined by SDS polyacrylamide gel electrophoresis and Ultrogel AcA 34 gel filtration was about 50,000. The enzyme showed a broad pH optimum ranging from 7.4 to 9.5. The Km values for D-glucose, D-fructose, 2-deoxy-D-glucose, D-mannose, D-glucosamine and ATP were 0.045, 4, 0.21, 0.05, 0.35 and 0.3 mM, respectively. N-Acetyl-D-glucosamine, D-xylose and D-galactose were not phosphorylated. The enzyme was strongly inhibited by the reaction products, glucose 6-phosphate and ADP, but not by high levels of D-glucose. The starfish hexokinase thus resembled mammalian isozyme A with respect to kinetic properties.
D000244:Adenosine Diphosphate / Q000494:pharmacology; D000818:Animals; D005958:Glucosephosphates / Q000494:pharmacology; D006593:Hexokinase / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008970:Molecular Weight; D013215:Starfish / Q000201:enzymology*; D013329:Structure-Activity Relationship
D005958:Glucosephosphates; D000244:Adenosine Diphosphate; D006593:Hexokinase