Properties of N-acetyl-beta-glucosaminidase in the masseter muscle of the mouse

The present study was undertaken to clarify various characteristics of N-acetyl-beta-glucosaminidase (NAG) in the masseter muscle of the mouse. The pH optimum of NAG in tissue homogenate was 4.3, and Km value for p-nitrophenyl-N-acetyl-beta-glucosaminide was 0.98 mM. By means of isoelectric focusing. NAG in the masseter muscle was separated into four enzymes (NAG I-IV). The isoelectric points were: I, 4.9; II, 6.4; III, 7.2 and IV, 8.7. The pH optima of NAG I-IV ranged from 4.2 to 4.4, and Km values from 0.61 to 0.83 mM. The molecular weights of I, II, III and IV were 135,000, 120,000, 135,000 and 110,000, respectively. Studies on heat stability showed that NAG I and IV were slightly labile as compared with II and III. The activities of NAG I-IV were dose dependently inhibited by both N-acetyl-glucosamine and N-acetyl-galactosamine. Both Ag and Hg2+ ions caused a marked inhibition on activities of NAG I-IV.