MITOCHONDRIAL MALIC ENZYME - SOURCE OF REDUCED NICOTINAMIDE ADENINE DINUCLEOTIDE PHOSPHATE FOR STEROID HYDROXYLATION IN BOVINE ADRENAL CORTEX MITOCHONDRIA

Studies have been carried out to determine the distribution of malic enzyme activity in bovine adrenal cortex. An enzyme which catalyzes this activity has been found in the mitochondrial fraction, differing in its chemical and kinetic properties from the cytosol enzyme. Some properties of these two enzymes are compared. Measurement of malic enzyme activity in the presence of dicumarol and dinitrophenol revealed that these respiratory uncouplers inhibited this activity. Measurements of intramitochondrial malic enzyme activity concomitant with 11β-hydroxylation in bovine adrenal cortex have been undertaken with malate and succinate as the source of reducing equivalents. The results obtained are considered to provide strong evidence that intramitochondrial malic enzyme activity is the major source of NADPH for 11β-hydroxylation in bovine adrenal cortex when either malate or succinate are the source of reducing equivalents. The role of malic enzymes in transferring reducing equivalents from the cytosol to mitochondria via a malate shuttle" is proposed. © 1969."