ALKALINE ISOMERIZATION OF HORSE AND YEAST CYTOCHROMES-C - SPECTROPHOTOMETRIC AND CIRCULAR-DICHROISM STUDIES

  • 1 January 1978
    • journal article
    • research article
    • Vol. 12  (5) , 233-236
Abstract
Spectrophotometric studies of the alkaline isomerization of horse heart and yeast cytochrome c (cyt c) show that the hemoproteins from Saccharomyces cerevisiae differ significantly from the mammalian cyt c. Apparent pKa values of 8.41, 8.40 and 8.73 for iso-1- (the methylated unmethylated forms) and iso-2-cyt c, respectively, from baker''s yeast were determined and compared with the value of 9.40 found for horse heart cyt c. The transitions, measured by observing the decrease of the absorbance at 695 nm as the pH increases, strictly parallel the decrease in amplitude of the negative circular dichroism band centered at 417 nm. This negative band may be closely related to the ligation of the heme Fe by the S atom of methionine 8.mu. for each of the 4 hemoproteins examined.

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