Tetrahydrobiopterin, a Cofactor in Mitochondrial Electron Transfer

Abstract

Submitochondrial particles, obtained from sonified rat liver and beef heart mitochondria, exhibit a strong increase of oxygen consumption in the presence of tetrahydropterin. As with to intact mitochondria, ultraviolet difference spectra indicate a concomitant reduction of cytochromes c and a/a 3 . A soluble electron transfer system, which consists of the essential components tetrahydropterin, cytochrome c , and cytochrome oxidase, is able to reduce molecular oxygen by NADH or NADPH. Submitochondrial particles and mitochondria are activated by cytochrome c in the same way, but less effectively. Radioactivity of 14 C‐labelled tetrahydrobiopterin is incorporated into mitochondria in the range of 1/4 to 2/3 of equilibrium distribution. The possible physiological function of tetrahydropterins in the control of cellular reducing power is discussed.