Purification and Properties of Hexokinase from the Starfish, Asterias amurensis

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Abstract
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 notby high levels of D-glucose.The starfish hexokinase thus resembled mammalian isozyme A with respect to kinetic properties.