Shark myoglobins I. Isolation and characterization of myoglobins from the sharks, Squalus japonicus and Proscyllium habereri.

Native oxymyoglobins from the sharks, Squalus japonicus and Proscyllium habereri were also isolated directly from red muscle. The essential step was the chromatographic separation of oxymyoglobin from metmyoglobin on a DEAE-cellulose column. The rate of autoxidation of native oxymyoglobin to metmyoglobin was examined over the pH range of 5-12 in 0.1 M buffer at 25 degrees C and the logarithms of the observed first-order rate constants, log (kobs), were plotted as a function of pH. The pH dependence for the autoxidation of Squalus myoglobin showed almost the same profile as those of bovine, sperm whale and yellowfin tuna myoglobins with distal histidines. On the other hand, the pH dependence of Proscyllium myoglobin differed remarkably from those of other myoglobins, especially in the absence of the proton-catalyzed processes in the acidic region of pH. These results suggest that Proscyllium myoglobin lacks distal histidine.