Enzyme-stabilizing activity of seed trypsin inhibitors during desiccation

Abstract

Seeds contain protective proteins which are able to preserve glucose-6- phosphate dehydrogenase (EC 1.1.1.49) activity upon co-dehydration of the enzyme with heat-stable seed protein extracts. Adenanthera pavonina L. (saga) seed extracts, in particular, have high levels of enzyme-preserving activity which not only alleviate the detrimental effects of desiccation in the presence of Tris-HCl and NaCl, but also stabilize enzyme activity in solution. Purification of Adenanthera seed extracts by reversed-phase and weak anion-exchange perfusion chromatography, followed by N-terminal protein sequencing have identified Kunitz-type trypsin inhibitors as the major proteins in one set of enzyme-preserving fractions. A quantitative comparison using various concentrations of purified proteins has demonstrated that soybean Kunitz trypsin inhibitor is as effective (on a mass basis) as bovine serum albumin in preserving enzyme activity, and may be an important protein permitting enzyme dehydration in a seed undergoing desiccation.