A basic trypsin- and chymotrypsin-inhibitor from groundnuts (Arachis hypogaea)

A trypsin- and chymotrypsin-inhibitor has been isolated by extraction of defatted groundnut meal at pH 5, by ammonium sulfate precipitation, and successive column chromatography on DEAE-cellulose, calcium phosphate, and CM-cellulose. The inhibitor was found to be homogeneous by ultracentrifugation, acrylamide gel electrophoresis, gel filtration on Sephadex G-50, and isoelectrofocusing in acrylamide gels. The pure inhibitor has an E_{1 cm}^{1 %} of 2.5 at 280 nm. Its isoelectric point lies between pH 8 and 9. Its molecular weight is about 7500. It is stable between pH 2 and 11 and stable in water when maintained at 100 °C for 15 min. The inhibitor forms stable complexes with trypsin and chymotrypsin at molar ratios of approximately 1:1. The phenomenon of temporary inhibition could not be observed. The complex of the inhibitor with either of the two enzymes fails to inhibit the other enzyme.