Abstract: Proteases from Mucor have a good market prospect in the production of soybean polypeptides for their high effectiveness in hydrolyzing soy protein and debittering hydrolyzed soy protein. In this work, we isolated and purified two acid proteases, Pa1 and Pa2 from Actinomucor elegans AS3.2778-fermented wheat bran by ammonium sulfate fractional precipitation, CM-Sephadex cation-exchange chromatography and phenyl-Sephadex hydrophobic chromatography. Pa1 and Pa2 were identified by SDS-PAGE analysis as monomeric enzymes with respective molecular weight of 35 ku and 33 ku. Pa1 had the highest activity at pH 5.5 and 50 ℃, and Pa2 at pH 4.5 and 50 ℃. Both enzymes showed good stability at temperatures below 40 ℃ and in acidic environment (pH 4.0－7.0) and were entirely inhibited by 10μmol/L pepstatin A, indicating that they belong to the aspartic protease family. Pa1 and Pa2 were weakly inhibited by Cu2+ and Zn2+ and Mn2+, Co2+ and Cu2+, respectively. The two enzymes had the same peptide bond selectivity complementary to that of alkaline protease Pb1 from Actinomucor elegans AS3.2778. The N-terminal amino acid sequence of Pa2 was GTGTVPVTDY, which was highly homologous to that of acid proteases from Rhizopus published in the NCBI database.

Key words: Actinomucor elegans, acidic proteases, purification, properties