Proteinase inhibitor(s) in seminal plasma of teleost fish

Anti‐proteinase activity has been found in seminal plasma of three teleost fish: rainbow trout, whitefish and yellow perch. The activity was effective against trypsin (bovine and cod) and acrosin (boar), but not bovine chymotrypsin. Inhibitor activity against fish trypsin was nine‐ to ten‐fold higher than against bovine trypsin. All anti‐proteinase activity remained in the retentate after filtration through molecular filter with 30 kDa cut‐off membrane and eluted from a column of Sephacryl S‐200 HR at the volume characteristic for molecular weight of approximately 90 kDa (data for rainbow trout). Inhibitor(s) had low thermal stability (50–60% activity remained after 15 min at 60° C). The discovery of proteinase inhibitor(s) in the seminal plasma of teleosts raised the question of the regulatory function of this protein in the systematic group of fishes having anacrosomal spermatozoa.