Gossypol prevents activation of purified proenzyme of human seminal plasma acidic proteinase

Gossypol inhibits the potential activity of the proenzyme form of human seminal plasma acidic proteinase, but has no effect on the active enzyme under the conditions tested. Inhibition of proenzyme is rapid and pH-dependent: 50% inhibition can be observed at gossypol concentrations of approx. 1.5 X 10(-5) M. SDS-polyacrylamide gel electrophoresis indicates that treatment of proenzyme with gossypol prevents the formation of active enzyme that normally occurs on acidification. Determination of free amino groups with 1-fluoro-2,4-dinitrobenzene suggests that gossypol reacts with 7.8 out of the 11.0 lysine residues in proenzyme: such a reaction could interfere with the activation process.