Crystalline Leghemoglobin. IX. Artificial Leghemoglobins.

Abstract

Artificial leghemoglobins have been prepared from mesohemin DC, deuterohemin IX, hematohemin DC, etiohemin III, pyrrohemin XV, pheophorbide [alpha]5 hemin, chlorin [alpha]6 hemin, and a mesoporphyringlobin complex from mesoporphyrin DC. The apopro-tein used in all the experiments was that of the slow component of leghemoglobin. All recombination reactions were performed in phosphate buffer, pH 7.0, [mu] equal to 0.1. The qualitative spectra for the artificial ferrileghemoglobins formed and those of their fluoride complexes are given. The spectral changes obtained with fluoride provides evidence of a combination through the hemin iron. The spectral differences observed with the 6,7-dipropionate hemins with different groups in positions 2 and 4 indicate that those groups have a function in combining the hemins to the apoprotein. The poor spectral extinctions as well as the low recombination yield obtained with etiohemin III, lacking carboxyl groups, stress the importance of the propionate groups in the recombination reaction. One propion-ate group seems to be enough to form a stable recombination compound, which was shown by the spectral changes of pyrrohemin as well as pheophorbide [alpha]5 hemin on combination. The specificity requirements for a hemin to recombine with apoleghemoglobin have been discussed.