Fructose diphosphatase from rabbit muscle: II. Amino acid composition and activation by sulfhydryl reagents

Abstract

The properties of rabbit muscle and rabbit liver fructose 1,6-diphosphatases are compared. It may be concluded that the two enzymes are different proteins with a number of common properties. They differ significantly in primary structure, as indicated by amino acid analysis, although there may be extensive homology. They are similarly activated by treatment with dinitrofluorobenzene or p-mercuribenzoate, or by disulfide exchange with 5,5′-dithio bis(2-nitrobenzoic) acid (DTNB). However, the muscle enzyme is not activated by cystamine, the only known natural activator of liver fructose diphosphatase. The enzyme activated with fluorodinitrobenzene retains normal sensitivity to the allosteric inhibitor AMP; after activation with DTNB the enzyme is somewhat less sensitive.