Bovine epididymal sperm proacrosin-acrosin system: quantification and partial characterization

Abstract

Several studies suggest that acrosin, an acrosomal trypsin-like serine proteinase, plays a role in fertilization. The enzyme is present in an enzymatically inactive precursor form, called proacrosin and is believed to be converted to the enzymatically active form(s) through one/multiple physiological event(s) prior to the sperm penetration of the zona pellucida. Although, the proacrosin-acrosin system of several species has been well documented, the study of the enzyme system in bovine caput and cauda epididymis (where the maturation of spermatozoa occurs) has not been characterized. The present study demonstrates the quantification and partial characterization of the proacrosin-acrosin proteinase system in unpurified acrosomal extracts of bovine caput and cauda epididymal sperm. Proacrosin activation followed the sigmoidal type of activation curve. Activation experiments demonstrate that almost 80-90y0 of this protein exists in zymogen (proacrosin) form either in ejaculated or caput and cauda epididymal spermatozoa. Time-course activation studies showed that the zymogen in isolated spermatozoa was completely converted to active non-zymogen form in 3 and 5 h after removal from the cauda and caput regions, respectively, at p H 8.0 at 25 "C. This conversion was markedly inhibited by calcium in a dose dependent manner and the inhibition was reversible. O n the other hand, calcium has a stimulatory effect on the hydrolytic activity of acrosin. These studies reveal that the proacrosinacrosin system can be identified in crude extracts of bull epididymal and ejaculated sperm.

Effect of Protease Inhibitors on the Acrosome Reaction and Sperm‐Zona Pellucida Binding in Bovine Sperm

“…1988). In cattle, this protease is mainly found in its proacrosin form, in caput and cauda epididymis as well as in ejaculated sperm (NagDas 1992). In ejaculated bovine sperm, proteolytic activity on gelatin substrates has been correlated with acrosin activity, which is blocked by protease inhibitors (Wendt et al.…”

Acrosin Activity Regulation by Protein Kinase C and Tyrosine Kinase in Bovine Sperm Acrosome Exocytosis Induced by Lysophosphatidylcholine

“…BAPNA (N‐α‐benzoyl‐DL‐arginine p ‐nitroanilide) was used as a specific acrosin substrate (NagDas 1992). To determine acrosin activity, the following sperm samples were prepared:…”

Proacrosin activation mechanisms in capacitated and frozen-thawed boar spermatozoa

“…Low fertilization rates of freeze-thawed spermatozoa are thought to be caused by damage to the spermatozoa (Bailey et al, 2000), including capacitation-like changes, which have been referred to as cryocapacitation (NagDas, 1992). Reports have shown that the sperm acrosome contains as many as 24 enzymes, including proteases and phospholipases; among them, acrosin is the most relevant to fertilization (Barros et al, 1996).…”