Amino acid content of rabbit acrosomal proteinase and its similarity to human trypsin.

Rabbit acrosomal proteinase from epididymal spermatozoa of 44 male rabbits was purified by subcellular fractionation, sucrose density gradient centrifugation, and electrofocusing; the specific activity of the purified product was 20,047 units per milligram, a value similar to that observed for pancreatic trypsins from various sources. The molecular weight determined from the amino acid analyses and ultracentrifugation was about 22,000. This rabbit acrosomal proteinase showed great similarity to pancreatic trypsin, especially to human pancreatic trypsin, both in the number of individual amino acids and in the total number of residues. This similarity was confirmed by an antigenic cross reaction between rabbit antiserum to bovine pancreatic trypsin with human, rabbit, rhesus monkey, and bull acrosotnal proteinase.