Methemoglobin reductase activity in fish erythrocytes

NADH-methemoglobin reductase activity of erythrocytes from the coho salmon, Oncorhynchus kisutch, sockeye salmon, Oncorhynchus nerka, and the rainbow trout, Salmo gairdneri exhibited a major band of activity that resembled the human enzyme in electrophoretic mobility. No polymorphism was found in 35 samples from rainbow trout, 4 samples from Dolly Varden, 29 samples from sockeye salmon, and 24 samples from coho salmon. All samples differed from the human enzyme in that they appeared to be membrane-bound and required the presence of a detergent, Triton X-100, for solubilization. Rainbow trout and coho salmon enzymatic activity is greater than the human enzyme activity at 15 degrees C.