Summary. A synthetic substrate (p-nitrophenyl-α-D-glucopyranoside) was used to measure the acid and neutral α-glucosidase activity in bull seminal plasma, spermatozoa and in homogenates of bull reproductive organs. Marked differences were observed in the activities of these enzymes in the various tissues studied. Epididymis and particularly its caput region contained the highest specific activity of acid αglucosidase. The activity of neutral α-glucosidase was highest in testis and in different parts of the epididymis. Seminal plasma, spermatozoa and seminal vesicle secretion contained only the acid enzyme activity.
After fractionation with anion exchange chromatography in HPLC (Mono Q) and chromatofocussing, acid α-glucosidase activity of seminal plasma was recovered in two fractions with different pI values. The corresponding activities were found in the secretion of seminal vesicles, which thus form the major secretory source of seminal plasma acid α-glucosidase. In the fractionation with gel filtration on Sepharose 6B, the acid α-glucosidase had a smaller molecular weight than did the neutral enzyme. In anion exchange chromatography and chromatofocussing the testicular and epididymal homogenates each contained two acid and two neutral isoenzymes. In both fractionations the elution pattern of acid α-glucosidase was clearly different from that of the enzymes in seminal plasma.
The pH optimum of acid α-glucosidase ranged from 3·75 to 4·5 and that of the neutral enzyme from 6·5 to 7·0. The neutral activity was more sensitive to many divalent metal ions and differences were also observed in the response of the enzymes to different concentrations of turanose and KCl.