Fish Liver Fructose 1,6-Diphosphatase: I. PURIFICATION OF THE ENZYME FROM GENYPTERUS CHILENSIS AND STUDIES ON ADENOSINE 5′-MONOPHOSPHATE INHIBITION

Abstract

Listen

Translate article

A method is described for the preparation of highly purified fructose 1,6-diphosphatase (EC 3.1.3.11) from the liver of the fish Genypterus chilensis. The purification procedure consists of only three steps, extraction at pH 3.5, ammonium sulfate fractionation, and P-cellulose chromatography. The purified enzyme appears to be homogeneous by the criteria of ultracentrifugation and disc gel electrophoresis. As with other fructose 1,6-diphosphatases, the fish liver enzyme shows allosteric AMP inhibition. The inhibition increases with decreasing temperature, and it is also increased by the presence of 150 m m KCl. However, the cooperative interaction among AMP binding sites is independent of temperature and potassium ions. When studied at the same temperature, fructose 1,6-diphosphatase from G. chilensis is much less sensitive to AMP inhibition than rabbit liver fructose 1,6-diphosphatase. However, a comparative study showed that the AMP inhibition curve obtained for the mammalian liver enzyme at 35° falls between the 5 and 15° experimental curves of the fish liver enzyme, in agreement with the physiological temperature range of G. chilensis (7 to 13°). These results are taken as an example of temperature adaptation at the enzymatic level in which a change in enzyme-effector affinity is sufficient to provide an efficient mechanism for the regulation of fructose 1,6-diphosphatase in this poikilotherm.