Abstract
THAT the hæm carboxyl groups might participate in reactions of hæmoproteins has received little attention, apparently because they were considered1,2 to be too far away to be affected by addition of ligands to the iron atom. It was suggested3 that the acid strength of hæm propionate side-chains might change, on the basis that substitution of R in RCH2CH2COOH has a significant effect on the pK value4 and that any alterations in the high state of resonance of the porphyrin ring system was likely to have the same effect as substitution of R. Further, since side-chain variation has a marked influence on the oxidation-reduction potential of the iron of hæmochromes2, it is, conversely, not unreasonable to expect that a change in electronic structure of the iron atom could effect the acid strength of the propionates.
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References
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O'HAGAN, J. Decrease in Acid Strength of Propionate Side-chains of Hæmatin on Reduction to Hæm. Nature 184, 1808 (1959). https://doi.org/10.1038/1841808a0
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DOI: https://doi.org/10.1038/1841808a0
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