抄録
Spectrophotometric titration of the tyrosyl groups of bovine heart, Saccharomyces oviformis, and Candida krusei ferricytochromes c was carried out by measuring the optical densities at 244mμ at various pH's. It was found that tyrosyl ionization of the three species of cytochromes c studied here is abnormal. From the optical rotatory dispersion studies, it was found that the conformation of the cytochrome c molecule is disrupted above pH 11.5 However, even the tyrosyl residues which ionize below pH 11.5 have abnormally high pK values. The titration curves of the tyrosyl residues of the three species of cytochromes c are different from each other. This suggests that the difference in the amino acid sequence in the linear structure may affect the ionization of the tyrosyl residues located at the same positions. The titration curve of Candida krusei ferrocytochrome c was located in a higher pH range than that of ferricytochrome c and about four of the five tyrosyl residues were titrared below pH 12.
