Enzymatic production of 5′-inosinic acid by AMP deaminase from a newly isolated Aspergillus oryzae

• The AMP deaminase from A. oryzae for 5′-inosinic acid (5′-IMP) production.
• The AMP deaminase production system could be effectively amplified.
• Crude enzyme catalyzed IMP production with the molar yield of 84.8%.

5′-adenylic acid deaminase (AMP deaminase), an important enzyme for the food industry, can catalyze the irreversible hydrolysis of adenosine monophosphate (AMP) to inosine monophosphate (IMP) and ammonia. In this study, a new strain was screened that efficiently produces 3191.6 U/g of AMP deaminase at 32 °C. After purification, the optimal temperature and pH of the AMP deaminase were found to be 40 °C and 6.0, respectively, but it was partially inhibited by Fe3+, Cu2+, Al3+, and Zn2+. With amplification of the AMP deaminase production system, 6 mL of crude enzyme could produce 2.00 mg/g of IMP from 2.04 mg/g of dried yeast with an 84.8% molar yield after 40 min. These results provide a new insight into AMP deaminase production and offer a potential platform for producing 5′-IMP.