Crystalline Leghemoglobin. IV. Spectroscopic Studies of the Two Main Metleghemoglobin Components and Some of their Fatty Acid Complexes.

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Abstract
The transition from acid to alkaline metleghemoglobin follows a monovalent dissociation curve. The pK values (at an ionic strength of 0.1) were determined spectrophotometrically and were found to be 8.16 for the electrophoretically faster moving component, and 8.34 for the slower one. No other hem linked groups were spectrophotometrically demonstrable between the pH values of 5.35 and 10.45. Acetate, propionate, butyrate and valerate were found to form reversible complexes with the two main metleghemoglobin components. The isosbestic points for the complexes were at 583 and 500[long dash]490 m[mu]. The pK values of the fatty acid complexes at pH 4.8 were pKacetate = 2.9, pKpropi-onate = 2.8, pKbutyrate = 2.4 and pKvalerate = 2.6. The pK values were essentially independent of the sizes of the alkyl groups. This has led to the conclusion that the hem is not buried within the folds of the apoprotein, but is attached to the surface of it.
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