Absorption spectral studies on heme ligand interactions of P-450nor.
Heme-external ligand interactions of P-450nor were examined spectrophotometrically and compared with those of other P-450s. Most nitrogenous ligands induced type II spectral changes on binding to ferric P-450nor, as did other P-450s. In contrast with other P-450s, 2-methylpyridine and 1-butanol induced type I changes in the spectrum of P-450nor. No spectral interaction of ferrous P-450nor with these ligands was observed. The absorption spectra of the alkyl isocyanide complexes of ferrous P-450nor exhibited the Soret peak at 427 nm with a slight shoulder at around 455 nm at neutral pH, and this shoulder was intensified as the pH was increased, suggesting that the isocyanide complexes of P-450nor existed in two states (the 430 and 455 nm states) which were in pH-dependent equilibrium in a similar manner to microsomal P-450s. However, the equilibrium was shifted mostly to the 430 nm state in the complexes of P-450nor. The findings suggest that P-450nor, especially its ferrous form, has some distinct features from P-450cam and microsomal P-450s in the distal heme environment.
Imai
Y
Y
Department of Veterinary Science, Osaka Prefecture University, Japan. imai@jyui.vet.osakafu-u.ac.jp
Okamoto
N
N
Nakahara
K
K
Shoun
H
H
D001667:Binding, Competitive; D019475:Camphor 5-Monooxygenase / Q000378:metabolism; D002248:Carbon Monoxide; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D005290:Ferric Compounds / Q000378:metabolism; D005296:Ferrous Compounds / Q000378:metabolism; D005670:Fusarium / Q000201:enzymology; D006418:Heme / Q000378:metabolism*; D007093:Imidazoles / Q000378:metabolism; D008024:Ligands; D009570:Nitriles / Q000378:metabolism; D010088:Oxidoreductases / Q000378:metabolism*; D011725:Pyridines / Q000378:metabolism; D013053:Spectrophotometry; D017186:Titrimetry
D005290:Ferric Compounds; D005296:Ferrous Compounds; D007093:Imidazoles; D008024:Ligands; D009570:Nitriles; D011725:Pyridines; C002990:butyl isocyanide; D006418:Heme; D002248:Carbon Monoxide; D003577:Cytochrome P-450 Enzyme System; D010088:Oxidoreductases; D019475:Camphor 5-Monooxygenase; C080610:nitric-oxide reductase (P450)