CHARACTERIZATION OF BETA-N-ACETYLGLUCOSAMINIDASE FROM HUMAN EPIDIDYMIS

beta-N-acetylglucosaminidase (NAG) activity in human epididymal fluid was separated into two forms (I and II) after HPLC-hydrophobic interac tion chromatography. Both forms exhibited maximal activity at a pH of around 4.5 and had a molecular weight of 125 kD when determined by Sup erose-HPLC. After incubation at 50 degrees C, form I retained only 30% of its activity while form II retained 90% activity. When analysed by non-denaturing electrophoresis, form I displayed higher electrophoret ic mobility than did form II. These features indicate that the I and I I isoforms found in the human epididymis are the A and B forms present in other tissues. NAG activity was measured in the fluid obtained for m the different epididymal regions of 13 different samples. An average four-fold increase in activity between the proximal caput and distal corpus was found. The contribution of each isoform to the total activi ty was studied. The proximal caput found to be rich in the A isoform ( 59%), whereas the B form was predominant in the distal corpus (65%). H uman spermatozoa contain membrane-associated NAG activity with an isof orm distribution similar to that found in cauda epididymal fluid (CEP, 80% B). Finally, enzyme activity in CEP was two-fold greater than in seminal plasma. Taken together these results suggest that NAG may beco me associated with human spermatozoa during epididymal transit.