Phospholipid synthesizing enzymes of dermatophytes. III. Glycerol kinase of dermatophytes.

Glycerol kinase, the key enzyme for glycerol use in phospholipid synthesis, was identified in cytosolic fractions of 2 dermatophytes, Microsporum gypseum and Epidermophyton floccosum. Ammonium sulfate was observed to activate and stabilize this enzyme in both dermatophytes. Two pH optima, 8.0 and 10.5, were observed for both dermatophyte enzymes. Glycerol kinase from M. gypseum was purified up to 33-fold with a 225% recovery by ammonium sulfate precipitation and gel filtration. The molecular weight of the enzyme was ca. 4.5 X 10(5). It had 2 pH optima of 8.0 and 10.5. The enzyme had Km values of 0.35 mM and 2.3 mM for glycerol and ATP. Reactivity of the enzyme for various nucleotides was ATP greater than TTP greater than GTP greater than ITP = CTP = UTP. Kinetic studies showed the enzyme to catalyze the reaction by the ping-pong mechanism. Fructose 1,6-bisphosphate and glucose-6-phosphate inhibited the enzyme competitively, whereas glucose was not inhibitory.