Angiotensin-converting enzyme and other peptidolytic enzymes in human semen and relations to its spermatologic parameters

Angiotensin-converting enzyme (ACE) and other enzymes of the renin-angiotensin system (RAS) occur in human semen in high activities. In contrast to bull ejaculates, not all zinc-dependent metallopeptidases are found to be in close correlation to the microscopically determined semen parameters; such a relationship was established only partly for the ACE. On the other hand, the RAS-dependent spermatozoa-bound enzymes, inclusive ACE, uniformly show negative correlations to the spermatologic parameters of human semen. These results, for the first time, point to different functions of the sperm-cell-bound (testicular) and of the seminal plasma (pulmonary) ACE activities.