Regulation of storage protein degradation in cotyledons of germinating cowpea

Storage protein degradation in cotyledons of germinating cowpeas begins after 24 h lag. Most rapid degradation occurs on 3rd and 4th day accompanied by rapid rise in protease activity and amino acid accumulation. Cotyledon extracts for proteases show activity peaks at pH 4.2 and 7 with Km values 0.096% and 0.227% BSA respectively and common 40°C temperature optima. Enzyme(s) active at both peaks require sulfhydryl groups. Acid protease(s) formation begins late but is more rapid and stage specific. It is progressively autodigested. All activity is lost at 144 h. Neutral protease(s) is more stable. About 60% initial activity is retained at abscission of cotyledons at 168 h. Probably acid protease(s) plays key role in reserve protein mobilization while neutral protease(s) plays greater role in cotyledonary senescence.