Reduction of Metmyoglobin by Extracts of Bovine Liver and Cardiac Muscle

Enzymatic reduction of metmyoglobin ( in vivo ) was investigated using a partially purified metmyoglobin reductase from bovine cardiac muscle. Greater substrate reduction (P<0.05) occurred at pH 6.3 versus 7.0 or 7.3 and at 375°C compared to 22°C using either partially purified cytochrome as or potassium ferrocyanide as reaction mediators. Differences in effectiveness between potassium ferrocyanide and the cytochrome b, preparation were dependent on specific pH/temperature conditions. The cytochrome preparation alone (i.e. without metmyoglobin reductase) reduced metmyoglobin at a rate comparable to that of the reductase. At 22°C the cytochrome b=, preparation assay displayed much slower re‐oxidation than the cardiac reductase/ferro‐cyanide assay (48 vs 2 hr, respectively).