Purification, properties, and kinetics of D-ribulokinase from Aerobacter aerogenes

The enzyme D-ribulokinase from Aerobacter aerogenes was purified to near homogeneity. The molecular weight, as determined by Sephacryl gel chromatography, is 116,000. The subunit molecular weight, determined by sodium dodecyl sulfate-gel electrophoresis, is 59,000, suggesting that D-ribulokinase is a dimer of identical subunits. Initial rate kinetic studies, involving substrate analogs and products, were carried out. These investigations support a kinetic mechanism of the Random Bi Bi type. Isotope partitioning, utilizing D-[3H]ribulose, indicates that the mechanism is steady state Random Bi Bi.