N-Acetylation of glucosamine-6-phosphate in Leuconostoc mesenteroides.

A partially purified enzyme (120-fold) from Leuconostoc mesenteroides catalyzed the reversible N-acetylation of d-glucosamine-6-phosphate. Coenzyme A was not required and inhibited the reaction rate. Neither d-glucosamine nor N-acetyl-d-glucosamine served as a substrate for the reversible reaction. The enzyme preparation retained 50% of its original activity after 5 min at 100 C. The K(m) for acetate was 7.7 x 10(-2)m in the presence of 2 x 10(-2)md-glucosamine-6-phosphate. The K(m) for d-glucosamine-6-phosphate was 5.0 x 10(-3)m in the presence of 0.64 m acetate. The product of the reaction was characterized by comparison with N-acetyl-d-glucosamine-6-phosphate prepared by enzymatic phosphorylation of N-acetyl-d-glusamine. The characterization tests were: chromatographic migration, acid hydrolysis, enzymatic dephosphorylation, sodium borohydride reduction, and periodate oxidation. The equilibrium constant for the reaction was about 7.5 m for the expression K = (d-glucosamine-6-phosphate)(acetate)/N-acetyl-d-glucosamine-6-phosphate. The standard free energy of the reaction was approximately 1,200 cal per mole.