Dog prostate arginine esterase is related to human prostate specific antigen

We have analyzed prostatic proteins of canine and human seminal plasma. We have compared in particular the physicochemical characteristics of arginine esterase from dog to those of the prostatic specific antigen from man. Both are major secretory proteins in each species. Arginine esterase and prostate specific antigen are related enzymes belonging to the serine-protease class. Their enzymatic activity towards protein substrates appears similar. However their activity towards synthetic substrates indicate that arginine esterase is a trypsin-like enzyme whereas prostate specific antigen has some chymotrypsin-like activity. The canine enzyme is inhibited by phenylmethylsulfonyl fluoride while the human one is not. The amino acid sequence of a portion of the NH2-terminal of the 2 proteins share 58% homology. Their molecular weights are similar: 29 KDa for arginine esterase and 34 KDa for prostate specific antigen. These results show that arginine esterase and prostate specific antigen are distinct but closely related proteins. These results strongly suggest that the dog could be an excellent model for the elucidation of the presently unknown role of this class of abundant enzymes of prostatic origin.