Comparative studies on the structures of the heat labile beta-N-acetylhexosaminidases from human plasma and placenta

Characterization of human salivary beta-N-acetyl-D-glucosaminidase (NAGase)

NAGase activity was studied in mixed whole, parotid, and submandibular saliva. The maximum activity of NAGase was found to be at pH 5.0. NAGase activity varied considerably among the subjects. The data indicated that a large portion of NAGase activity originates from oral microorganisms. NAGase activity was greatly reduced after heating for 45 min at 50 degrees C. The residual activity after storage at -20 degrees C was higher than the original activity. The enzyme activity was markedly diminished after the addition of Sn++ and Ag+ ions, while no activity was detected after the addition of Hg+ ion.

beta-N-acetyl-D-glucosaminidase (NAGase) and lysozyme activity in human parotid and submandibular saliva

beta-N-acetyl-D-glucosaminidase (NAGase) and lysozyme activity were studied in isolated parotid and submandibular saliva collected from five healthy individuals over a 3-wk period. During the first week, saliva samples were collected three times within one specified day (9 a.m., noon, 4 p.m.). Then for each of the following 2 wk, saliva was collected at 9 a.m. of the same day. NAGase activity was determined spectrophotometrically by using p-nitrophenyl-glycoside as substrate. Lysozyme activity was determined turbidimetrically by using Micrococcus lysodeikticus cells as substrate. NAGase and lysozyme were present in all samples of parotid and submandibular saliva. NAGase activity was generally higher in saliva samples collected in the morning and decreased during the day. There was considerable variation in NAGase activity and almost no variation in lysozyme activity in samples taken from the same person. NAGase activity was higher in parotid than in submandibular saliva while lysozyme activity was somewhat higher in submandibular saliva.