The presence of trypsin inhibitors is demonstrated in cotyledonary albumins of Vigna unguiculata by cross-electrophoresis against trypsin and by kinetic measurements. These inhibitors are isolated by selective trapping on insoluble trypsin. On the other hand, evidence is given showing that cotyledonary albumins hydrolyse α-N-benzoyl-DL-arginine-p-nitroanilide (BAPA) and casein. Purified trypsin-inhibitors partially inhibit the caseolytic activity of albumins but do not influence their hydrolytic activity toward BAPA. A partial characterisation of proteases and inhibitors is carried out. A model for the regulation of the proteolytic activities of the seeds by trypsin inhibitors is suggested.

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Cotyledonary cells are submitted to fractionation by isopycnic centrifugation. Small intact protein bodies are collected in the densest zones (d=1.205-1.237 g/cm(3)). Fragments of larger bodies are gathered in zones of lower density (d=1.205 g/cm(3)). Small dense bodies are largely sedimentable after dilution, whereas fragments of the large bodies dissociate into a dense sedimentable clot and into floating elements which contain most of the globulins and all of the albumins. Among the dissociated floating components are the BAPA-active endopeptidases and the trypsin inhibitors (BAPA=α-N-benzoyl-DL-arginine-p-nitroanilide). A caseolytic activity remains with the dense mass. The localisation of the albumins, globulins, proteases and trypsin inhibitors is discussed. Relations between solubility, structure and function are considered.

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