Abstract:

To study enzymatic properties of chymosin from Mucor pusillus (HL-1), the optimal temperature, pH and thermal stability of chymosin were investigated. Along with this, the effects of metal ions, chemical materials, calcium ions and enzyme amount on the activity of the enzyme were examined, and the proteolytic activity, relative molecular weight, Km and Vm of the enzyme were measured. The optimal reaction temperature and pH of the enzyme was 60 ℃ and 5.5. Incubation at 65 ℃ for 5 min resulted in 95% loss of enzyme activity. Calcium ion, an enzyme activator, could improve the enzyme activity in a concentration-dependent manner; in contrast, potassium ion was an inhibitor of the enzyme. Sodium chloride did not affect the enzyme activity, but SDS led to the severe inactivation of the enzyme. Meanwhile, a negative relationship between enzyme amount and reaction time was observed. The proteolytic activity, relative molecular mass, Km and Vm of the enzyme were 485.3 U/g, 42000, 0.0238 mol/L and 1.1227 mg/min, respectively.

Key words: Mucor pusillus (HL-1), chymosin, enzymatic properties