The major androgen‐dependent protease in dog prostate belongs to the kallikrein family: confirmation by partial amino acid sequencing

Canine prostate fluids and seminal plasma contain a major androgen-dependent protein which was identified as a proteolytic enzyme exhibiting an Arg-esterase activity. This protease, as characterized, is shown to be present as a two-chain structure held together by at least one disulfide bridge and composed of approximately 220 amino acids. Amino acid sequence determination of both chains has revealed a clear homology to other known amino acid sequences of serine proteases. Furthermore, the comparison of the presented 58 amino acids of the Arg-esterase with the other sequences revealed a very strong homology (larger than 50%) to members of the kallikrein family. The two chain structure could thus result from autolysis of a single chain enzyme in the 'kallikrein autolysis loop'. Amino acid composition of the canine prostatic enzyme suggests that it is related, but not identical, to pancreatic canine kallikrein.