Purification and Properties of an Extracellular Aminopeptidase from Streptomyces Lividans 1326

Summary: Streptomyces lividans was investigated for extracellular proteinases. The major extracellular proteinase activity detected under all conditions tested was L-leucine aminopeptidase activity. Slight extracellular L-proline aminopeptidase activity was also detected. No clear evidence for the presence of serine proteinases in S. lividans culture broths was found using several different methods. The major extracellular proteinase of S. lividans, i.e. the L-leucine aminopeptidase, was purified 33-fold to homogeneity. The purified enzyme was found by SDS-PAGE to have an M r of 34000. The purified enzyme had a final specific activity of 3·6 units mg−1, a K m for L-leucine-p-nitroanilide of 300 μM and a V max of 4·2 μmol min−1 mg−1. The pure enzyme did not exhibit proteolytic activity on azocasein or L-proline-p-nitroanilide, substrates for other proteinase activities observed in crude extracts of S. lividans.