Inosine-5′-monophosphate (5′-IMP) and guanosine-5′-monophosphate (5′-GMP), used as flavor enhancers in food processing, are hydrolyzed by phosphatases in foods. The studies on the phosphatases in watersoluble fraction of animal meat were carried out. The water-soluble fraction of animal meat contains acid phosphatase with optimum pH 5-6. In general, this activity is accelerated by Mg++, Mn++, Ni++ and Co++ and inhibited by Zn++. This phosphatase acts on 2′ (3′) -AMP and β-glycerophosphate as well as on 5′-nucleotides. This is inactivated by the heating at 70°C for 5 minutes.
Following the preceding paper, studies were carried out on the properties of phosphatases in the water-soluble fraction of fish meat. In the water-soluble fraction of fish meat, there are both acid and alkaline phosphatases. The acid phosphatase has similar properties to that of animal meat. The alkaline phosphatase has optimum pH at about 9. The alkaline phosphatase is inhibited by Zn++, but not affected by Mg++, Mn++, Ni++ and Co++ significantly. This phosphatase acts on 5′-nucleotides, but is less active on 2′ (3′) -AMP and β-glyceraphosphate. Both acid and alkaline phosphatases are inactivated by heating at 70°C for 5 minutes. The relationship between heating velocity and the degradation of 5′-IMP was discussed.