Cofactor Requirements for Oxidation of Alpha-Keto Acids by Sweet Potato Mitochondria.

Abstract

Mitochondria isolated from sweet potatoes oxidized most Krebs cycle acids in the presence of AMP, Mg, glucose, and phosphate, but could not oxidize pyruvate. The addition of the cofactors DPT and DPN to the reaction mixture brought about high rates of pyruvate oxidation. Oxidation of [alpha]-ketoglutarate was increased more than 200% by addition of DPT, DPN, and CoA. Exogenous lipoic acid had no effect with pyruvate or [alpha]-ketoglutarate as substrate. However, arsenite completely inhibited oxidation of both a-keto acids indicating the possible presence of lipoic acid in the mitochondria. Chromatographic evidence suggests that oxidation of the [alpha]-keto acids by these mitochondria is mediated through the Krebs cycle.