Evidence for formation of a rabbit liver aldolase--rabbit liver fructose-1,6-bisphosphatase complex.

Abstract

The ability of rabbit liver aldolase (EC 4.1.2.13) and rabbit liver fructose-1,6-bisphosphatase (Fru-P2ase, (EC 3.1.3.11)) to partition into the gel phase of Ultrogel AcA 34 is decreased in a mixture of the 2 enzymes. Titration experiments indicate that a 1:1 complex is formed. The value for the distribution coefficient of the complex corresponds to a molecular mass of 300,000 daltons, the value expected for a dimer containing 1 mole of each enzyme protein. Complex formation was not observed when either liver enzyme was replaced by the corresponding isozyme from rabbit muscle. The susceptibility of liver Fru-P2ase to limited proteolysis by subtilisin was reduced in the presence of liver aldolase, but not when the latter was replaced by muscle aldolase, suggesting that the conformation of Fru-P2ase is altered in the complex. Limited proteolysis of liver aldolase abolishes its ability to form the heterodimer and to protect Fru-P2ase from modification by subtilisin.