An inhibitor of trypsin and chymotrypsin was purified from horse gram (Dolichos biflorus) beans. The concentration of the inhibitor which provided total inhibition was 0.27 Μg/Μg tryptic enzyme and 0.46 Μg/Μg chymotryptic enzyme. The inhibitor was stable at 37‡C between pH of 3 to 11 and at 97‡C, upto pH 5.0 only. While the activities were rapidly lost in 0.1N NaO H the loss was only 5 0% in 0.1N HCl when kept for 2 h at 97‡C. On heating at pH 7.8, it remained stable upto 80‡C with a gradual loss in activities at 97‡C and a total loss occurring by autoclaving at 15 psi for 10 min. Reduction of disulphide bonds by 2-mercapto-ethanol, pronase digestion and boiling in the presence of 1 M NaCl led to reduction in the activities. However, the inhibitor was resistant to the action of pepsin and subtilisin and to urea at 37‡C.

Purification and characterization of proteases from developing normal maize endosperm and high lysine opaque-2 maize endosperm have been carried out with a view to understand their role in storage protein modification. At day 15, normal maize endosperm had two types of proteolytic enzymes, namely, protease I and protease II, while at day 25 protease n disappeared and in place protease III appeared. However, in opaque-2 maize endosperm at both the stages only one type of enzyme (protease I) was present. These proteases had many properties in common-optimum pH and temperature were respectively, 5.7and 40°C; their activity was inhibited to the extent of 75 –93 % by p-chloromercuribenzoate; trypsin inhibitor inhibited the activity more at early stages of endosperm development; all proteases cleaved synthetic substrates p-tosyl-L-arginine methylesler and N-benzoyl-L-tyrosine ethyl ester and poly-L-glutamic acid. TheKm values of day 15 and 25 normal maize endosperm proteases ranged from 2.73–3.30, while for opaque-2 maize endosperm protease I it was 3.33 mg azocasein per ml assay medium. These enzymes, however, differed with respect to proteolytic activity towards poly-L-lysine. Only normal maize endosperm protease III at day 25 followed by protease II at day 15 showed high activity towards this homopolypeptide suggesting thereby their role in determining the quality of normal maize endosperm protein.

Activity of key nitrogen assimilating enzymes was studied in developing grains of high-lysine opaque sorghum P-721 and normal sorghum CSV-5. The higher percentage of protein in opaque sorghum was mainly due to lower starch content since protein per grain was less than in CSV-5. During grain development, albufn and globulin decreased while prolafne and glutelin increased. Prolafne content in CSV-5 was higher than in opaque sorghum. Average nitrate reductase activity in flag and long leaf were similar in both the varieties. The nitrate reductase activity decreased during grain development. Glutamate dehydrogenase activity was higher during early development and lower at later stages in opaque sorghum than in CSV-5. Glutamate oxaloacetate transaminase activity was higher and glutamine synthetase lower in opaque sorghum than in CSV-5 grains during development. Glutamate synthase activity was higher in opaque sorghum up to day 20 and lower thereafter than in CSV-5. It is suggested that reduced activities of glutamine synthetase as well as glutamate synthase in opaque sorghum as compared to CSV-5 during later stages of development may restrict protein accumulation in the former.