Glycerol kinase
Glycerol kinase (GK) has been purified and its kinetic properties have been examined (Krakow and Wang, 1990). It is a monomeric protein with molecular mass of approximately 53,000. It has a broad pH optimum between pH 7 and 9.5 and catalyses a random bi bi reaction, with some cooperativity in substrate binding at high pH. Glycerol-3-phosphate up to 10 mM displays virtually no product inhibition of the forward reaction, but ADP is a weak inhibitor. The reverse reaction, essential for anaerobic glycolysis, proceeds at an extremely low rate and only in the presence of an efficient ATP trap. This is in agreement with the idea that the enzyme reaction is reversed by mass action only.