Some Characteristics of the Enzymic Lipid Peroxidation System in the Microsomal Fraction of Flounder Skeletal Muscle

Abstract

ABSTRACT The microsomal lipid peroxidation system of flounder muscle was characterized as to response to temperature, cofactor requirements, inhibitors, and activators. The enzyme‐catalyzed reaction had a ratelimiting step prior to the formation of lipid hydroperoxides. The K M for NADH of the enzymic system in the presence of 0.1 mM ADP was approximately 1 μM. In the presence of Fe +3 both cysteine and ascorbate also catalyzed lipid peroxidation. While neither NADH nor ADP had an effect in the presence of ascorbate‐Fe +3 , NADH stimulated the cysteine‐Fe +3 oxidation and ADP completely inhibited it. Inhibitor studies indicated that it was a free radical reaction, an ‐SH group was involved and O 2 reduction products and singlet oxygen participated.