SERINE PROTEINASE FROM RICE BEAN

A trypsin like serine-proteinase of M(r) 16,000 Da, optimally active a t pH 8.4 on N-benzoyl-arginine ethyl ester (BAEE) was purified from 4- day old germinated seeds of rice bean, Vigna umbellata (Thunb), by amm onium sulphate precipitation, gel filtration, ion-exchange chromatogra phy and by high performance liquid chromatography (HPLC). The purity o f the enzyme was checked by polyacrylamide gel electrophoresis (PAGE). The enzyme activity was studied on natural substrates like casein, ha emoglobin and vicilin, a rice bean storage protein. The activity of th e enzyme was completely inhibited by phenylmethylsulfonyl fluoride, bu t not by iodoacetamide and HgCl2, suggesting it to be a serine proteas e. Loss of activity in presence of EDTA was reversed by addition of Ca 2+.