Further data on mitochondrial malic enzyme in man.

Mitochondrial malic enzyme was examined by starch-gel electrophoresis in human brain samples from 291 adults and 118 fetuses, all of European origin. Gene frequencies were estimated as MEM1 0.65 and MEM2 0.35. There was no significant difference in phenotype distribution between the sexes nor between adults and fetuses. No deviation from Hardy-Weinberg equilibrium was found. Malic enzyme was examined in various other tissues and although strongest in brain, it was also frequently active in adult testis, heart and kidney. An additional isozyme migrating less anodally than mitochondrial malic enzyme and especially prominent in heart muscle was found to be attributable to a combination of aconitase and isocitrate dehydrogenase acting on citrate in the gel buffer.