Isoenzyme pattern of lactate dehydrogenase associated with human prostasomes

Lactate dehydrogenase (LD, EC 1.1.1.27) activity was determined in serum, seminal plasma and prostasomes from normozoospermic and azoospermic (due to vasectomy) men. A 10-fold higher activity was noted in seminal plasma as compared with serum. LD activity was enriched in prostasomes although a fairly large amount of enzyme activity seemed to be free in solution. Isoenzymes LD1, LD2 and LD3, present in prostasomes in about equal amounts, gave rise to a characteristic isoenzyme pattern that differed distinctly from that found in seminal plasma of normozoospermic men, the main isoenzyme of which was LD-X.