title: Cysteine proteinase inhibitor levels in semen.
abstract: New proteinase inhibitors have recently been found in seminal plasma which specifically inhibit cysteine proteinases such as ficin, papain, cathepsin H and cathepsin B. The inhibitors consist of two components, In-A and In-B, both of which are effective in native semen. In the present work, a method of assay is devised to determine activities of both components separately. Under conditions in which In-B is denatured completely while In-A is not, inhibitory activity of In-A alone is determined. The mean In-A inhibitory level is 1.52 +/- 0.28 inhibitor unit/mL and the level is independent of the number of spermatozoa. In-B level is calculated by subtracting In-A level from the total ficin inhibition level of the semen. The mean In-B level is 1.47 +/- 0.52 inhibitor unit/ml. In-B level has a tendency to increase with increasing number of spermatozoa. The correlation coefficient is 0.307 and statistical significance p less than 0.005.
mesh_terms: D004796:Clinical Enzyme Tests / Q000379:methods; D003546:Cysteine Endopeptidases; D015853:Cysteine Proteinase Inhibitors; D010450:Endopeptidases; D006801:Humans; D007525:Isoelectric Focusing; D008297:Male; D011480:Protease Inhibitors / Q000032:analysis*; D011506:Proteins / Q000032:analysis*; D012661:Semen / Q000201:enzymology*; D013076:Sperm Count; D013094:Spermatozoa / Q000201:enzymology; D013379:Substrate Specificity
chemical_list: D015853:Cysteine Proteinase Inhibitors; D011480:Protease Inhibitors; D011506:Proteins; D010450:Endopeptidases; D003546:Cysteine Endopeptidases