MOLECULAR AND ENZYMATIC-PROPERTIES OF AN ASPARTIC PROTEINASE FROM RHIZOPUS HANGCHOW

An aspartic proteinase, rhizopuspepsin (EC 3.4.23.21), from Rhizopus h angchow was purified. The M(r) and isoelectric point were determined a s ca 37000 and 4.5, respectively. The first 19 amino acids in the N-te rminal region were SGSGVVPMTDYEYDIEYYG. The contents of the alpha-heli x, beta-structure and random coil were calculated to be ca 7.5, 88.9 a nd 2.7%, respectively. The enzyme can activate trypsinogen at pH 3.0. The activity was completely inactivated by pepstatin A. The specificit y and mode of action of the enzyme were investigated with oxidized ins ulin B-chain at pH 3. The enzyme hydrolysed primarily two peptide bond s, the Leu(15)-Tyr(16) bond and the Tyr(16)-Leu(17) bond, while additi onal cleavage of the bonds, Ala(14)-Leu(15) and Phe(24)-Phe(25) was al so noted.