Studies on Algal Cytochrome Ii Physico-Chemical Properties of Crystalline Porphyra Tenera Cytochrome 553

The Physico-chemical properties of an algal cytochrome, Porphyra tenera cytochrome 553 were investigated, using a crystalline preparation of the substance. The cytochrome was found to be highly resistant to heat and preservation. The stability of the cytochrome was also prominent in a wide range of pH. Absorption spectra as: well as data concerning the extinction coefficients of the oxidized and reduced forms are presented. The oxidation-reduction potential of the cytochrome was determined at various pH. The value for the normal potential was found to decrease gradually with increasing pH; from 355 mV at pH 5.0, to 270 mV at pH 11.0. Electrophoretic investigation revealed that this cytochrome is a markedly acidic protein, with an isoelectric point of pH 3.5. The molecular weight of the cytochrome was determined from ultracentrifugal and diffusion experiments to be 13,600. The values for the minimum molecular weight calculated from the heme- and iron-contents are, respectively, 12,000 and 11,000.