A NEW B-TYPE CYTOCHROME FROM WHITEFISH (COREGONIDAE) EGGS

A new low-spin, high-potential, water-soluble b-type cytochrome was is olated from whitefish egg yolk. The cytochrome is termed b(560) accord ing to the alpha-maximum in its difference (reduced-minus-oxidized) ab sorption spectra. The absolute absorption spectrum of the reduced cyto chrome measured at 20 degrees C has three characteristic maxima at 426 , 529, and 561 nm At 20 degrees C the oxidized form of the cytochrome has a maximum in its gamma-spectral region at 416 nm. The difference s pectrum of the cytochrome (reduced-minus-oxidized) has three character istic maxima at 428, 529, and 560 nm. The midpoint redox potential of the cytochrome is +193 mV and its molecular weight is 20.4 kD as indic ated by electrophoresis under denaturing conditions. The reduced cytoc hrome binds neither CO nor CN- and is oxidized by oxygen and hydrogen peroxide with oxidation half-times of 28 and 2.4 min, respectively The oxidized cytochrome is not reduced by cytochrome c or NAD(P)H but can be rapidly reduced by sodium ascorbate.