Endergonic reduction of mitochondrial diphosphopyridine nucleotide by sarcosine.

The aerobic dehydrogenation of the N-methyl group of sarcosine initiates an energy-requiring reduction of diphosphopyridine nucleotide in intact mitochondria. The formation of DPNH can be measured both spectrophotometrically and by the reduction of acetoacetate. Except in the presence of uncouplers, such as Dicumarol and arsenate, reduction of DPN by sarcosine does not require added adenosine triphosphate. The formation of DPNH is inhibited by Amytal, but not by oligomycin. It is proposed that DPN is reduced by electron transfer flavoprotein(2H) via the Amytal-sensitive site of the respiratory chain, and that the energy for this endergonic process can be transferred from the two terminal sites of energy conservation without the participation of inorganic phosphate.