Tetrahydrobiopterin, a Cofactor in Mitochondrial Electron Transfer: A Soluble Transfer System

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/a3. 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 14C‐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. Copyright © 1972, Wiley Blackwell. All rights reserved