Bovine heart malic enzyme. I. Isolation and partial purification of a cytoplasmic and a mitochondrial enzyme.

Homogenates prepared from bovine heart muscle contain two distinct forms of malic enzyme (malate:NADP+ oxidoreductase (decarboxylating), EC 1.1.1.40), which can be easily separated by chromatography on DEAE-cellulose. A partial purflcation of the two enzymes has been accomplished by means of DEAE-cellulose chromatography, ammonium sulfate fractionation, and chromatography on CMSephadex. The isolated fractions migrate at different rates on disc gel electrophoresis and appear to have a similar molecular weight (approximately 200,000) as determined by sucrose density gradient centrifugation and gel filtration. Malic enzyme has also been purified from isolated bovine heart mitochondria, and all the properties of this enzyme correspond to one of the forms isolated from the homogenate. On the basis of these observations, it is concluded that malic enzyme is present in both the cytosol and the mitochondria of bovine heart, a distribution similar to that observed in bovine adrenal cortex but clearly distinct from that of liver.