Cellular origin, complementary deoxyribonucleic acid and N-terminal amino acid sequences of human seminal progastricsin.

The aspartic protease progastricsin (EC 3.4.23.3) is found in all parts of the mammalian stomach and has also been found extragastrically. In humans and monkeys, seminal fluid usually contains high concentrations of progastricsin. Using immunohistochemistry and in situ hybridization, we determined in this investigation the origin of seminal progastricsin to be the epithelia of both the prostatic gland and the seminal vesicles. In addition, Northern (RNA) blotting showed the presence of a 1.8-kb transcript in both tissues. Seminal progastricsin clones from two human prostatic gland cDNA libraries were isolated and sequenced. The combined sequence manifested only six nucleotide differences from the published genomic and gastric cDNA sequence. One conservative base substitution was present in both libraries. N-Terminal amino acid sequencing of all 43 residues of the seminal proenzyme and the first 34 residues of the mature enzyme yielded sequences identical to those deduced from cDNAs derived from both gastric and prostatic origin. The results obtained indicate that gastric and seminal progastricsin are products of the same gene and that the observed molecular differences between the zymogen from the two sources are probably due to posttranslational modifications.