[A study of the interaction of substrates with cytochrome P-450 by a method of UV- and 1H-NMR spectroscopy].

Acceleration of substrate longitudinal relaxation (T1) was used to study cytochrome P-450-aminopyrine (1st type substrate) and P-450-4-methoxypyridine (2nd type substrate) complexes. Dissociation constant, T1 and/or residence time of substrate in the complex can be obtained from the dependence of T1 of substrate protons on substrate concentration. Basing on the relaxation times, distances between Fe3+ ion in the active site and protons of the substrate moiety were determined. For aminopyrine all the distances proved to be about 8 A. In the P-450-4-methoxypyridine complex the pyridine nitrogen is directed towards Fe3+ ion. Cytochrome P-450 is compared with its denatured form, cytochrome P-420, and metmyoglobin.