Localization of metmyoglobin-reducing enzyme (NADH-cytochrome b(5) reductase) system components in bovine skeletal muscle.

Localization of metmyoglobin-reducing enzyme system components (NADH-cytochrome b(5) reductase, cytochrome b(5) outer mitochondrial membrane cytochrome b) was demonstrated in bovine skeletal muscle by immunohistochemical techniques. Both NADH-cytochrome b(5) reductase and OM cytochrome b were located in red fibers. However, localization of cytochrome b(5) did not show a definite difference between fiber types. Using an immunoblotting technique. NADH-cytochrome b(5) reductase was found predominantly in the mitochondrial fraction, but it was also detected at lower levels in the microsomal fraction. OM cytochrome b was found predominantly in the mitochondrial fraction, but cytochrome b(5) was detected only in the microsomal fraction. The results from this study, along with previous work about the localization of myoglobin in muscle, suggest that NADH-cytochrome b(5) reductase reduces metmyoglobin by using OM cytochrome b at the mitochondrial surface and, in part, by using cytochrome b(5) at the sarcoplasmic reticulum.