Characterisation of acid protease expressed from Aspergillus oryzae MTCC 5341

Aspergillus oryzae (MTCC 5341) has the largest expanse of hydrolytic genes, that includes 135 protease genes coding for alkaline, acid as well as neutral proteases. This study reports the purification and characterisation of an acid protease obtained from A. oryzae MTCC 5341. A. oryzae MTCC 5341 produces one of the highest reported acid protease activities reported so far (8.3 × 10⁵ U/g dry bran). The extracellular acid protease (47 kDa) was found to be active in the pH range 3.0–4.0 and stable in the pH range 2.5–6.5. Optimum temperature for activity was 55 °C. The protease was purified 17–fold with a yield of 29%. The enzyme was characterised to be an aspartate protease by inhibition studies, using pepstatin and its ability to activate trypsinogen. The enzyme cleaved the B-chain of insulin at L–V and Y–T residues.