Phospholipid synthesizing enzymes of dermatophytes: II. Characterization of choline kinase.

Choline kinase was located in the cytosolic fractions of the filamentous, pathogenic fungi,Microsporum gypseum andEpidermophyton floccosum. A broad pH optima (6.0-9.0) was observed for theM. gypseum enzyme, but theE. floccosum enzyme was active at pH 8.4 as well as 10.5, the activity being higher at pH 8.4. Enzyme from both dermatophytes had Km value of 3.3×10(-4) M for choline; however, for ATP, it was 6.6×10(-4) M and 12.6×10(-4) M forM gypseum andE. floccosum, respectively. Choline kinase of both dermatophytes showed SH-group requirement. TheM. gypseum choline kinase was inhibited to a greater extent by Mn(2+), Ca(2+) and Ba(2+) than was theE. floccosum enzyme. In comparison to other nucleotides, ATP was the most effective phosphate donor for phosphorylating choline in both dermatophytes. Higher concentrations of ATP inhibited the enzyme inM. gypseum as well asE. floccosum. Phosphorylcholine inhibited the choline kinase activity from both fungi, whereas phosphoethanolamine and glycerol 3-phosphate were stimulatory.