| Popis: |
Fructose 1,6-diphosphatase has been partially purified from the liver of the carp, Cyprinus carpio. The enzyme shows the general characteristics of the native form of most fructose 1,6-diphosphatases: maximal activity at neutral pH; high degree of specificity for its substrate, fructose 1,6-diphosphate; requirement for a divalent cation (Mg2+ or Mn2+); activation by monovalent cations (K+ or NH4+); inhibition by AMP. The inhibition by AMP is of allosteric nature, and it is increased by the presence of the monovalent cation activators. The AMP inhibition of carp liver fructose 1,6-diphosphatase is also temperature-dependent. In the range studied (5–25°), a decrease in temperature of 10° causes a 3.3-fold increase in AMP inhibition. However, by studying the interacting effects of pH and temperature, it is demonstrated that the AMP inhibition of carp liver fructose 1,6-diphosphatase can become nearly temperature-independent. The implications of these findings, and of our previous data on AMP inhibition of fish (Genypterus chilensis) liver fructose 1,6-diphosphatase (Gonzalez, A. M., Gonzalez, F., Golf, S., and Marcus, F. (1972) J. Biol. Chem. 247, 6067–6070), are discussed in terms of temperature adaptation of control mechanisms in poikilotherms. |
