Haem degradation in human haemoglobin in vitro. Separation of the contribution of the alpha- and beta-subunits.

Human haemoglobin was prepared containing [14C]haem in either the alpha- or the beta-subunits. Coupled oxidation of such hybrid haemoglobins with ascorbate and O2 showed that the biliverdin produced by the alpha-subunits contained approx. 55% alpha-isomer and 45% beta-isomer, whereas that produced by the beta-subunits contained approx. 75% alpha-isomer and 25% beta-isomer. Coupled oxidation of isolated alpha- and beta-subunits gave approx. 70% alpha-isomer, 30% beta-isomer and 78% alpha-isomer, 22% beta-isomer respectively. These results are consistent with calculations of differences in the haem environment in the two subunit types.