Glucose-6-phosphatase temperature

The effects of temperature both on the stability of the enzyme (26, 37, 41, 46) and on the catalytic reaction itself (46, 112) have been studied. The enzyme is considerably more labile to mild heating in the absence of substrates than is microsomal acid phosphatase (26, 37, 4U 46)-Glucose-6-P (26, 136), P, (26), glucose (136), PP, (119, 136), and various amino acids (136) protect to some degree against thermal inactivation as do certain metal chelators which inhibit the reaction (120). 

Many enzymes, however, do not show temperature compensation in their activities (Eckberg, 1962 Precht, 1964 Vellas, 1965 Hebb etal., 1969 Hazel and Prosser, 1970 Shkorbatov et al., 1972 Hochachka and Somero, 1973 Penny and Goldspink, 1981). Among these are catalase, peroxidase, acid phosphatase, D-amino acid oxidase, choline acetyltransferase, acetylcholinesterase and glucose-6-phosphate dehydrogenase. What is more, the same enzyme can show opposing temperature dependencies when examined in different organs and tissues of fish (Romanenko etal., 1991). 

Figure 5.2. Dependence of the relative rates of various processes on water activity at constant temperature. Curve 1 relative destruction rate of chlorophyll in spinach at 37°C. Curve 2 relative decay rate of ascorbic acid. Curve 3 relative oxidation rate of potato chips stored at 37°C. Curve 4 relative rate of inactivation of phosphatase in skim milk. Curve 5 relative rate of inactivation of Clostridium botulinum. Curve 6 drying rate of a slab of glucose at 30°C slab temperature. (From Thijssen, 1979.)...

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