Formation of iron(II)-nitrosoalkane complexes: A new activity of microperoxidase 8

Microperoxidase 8 (MP8) is a heme octapeptide, obtained by enzymatic hydrol ysis of heart cytochrome c, in which a histidine is axially coordinated to the heme iron, and acts as its fifth ligand. It exhibits two hinds of activ ities: a peroxidase-like activity and a cytochrome P450-like activity. We h ere show that MP8 is not only able to oxidize various aliphatic and aromati c hydroxylamines with the formation of MP8-Fe(II)nitrosoalkane or -arene co mplexes absorbing around 414 nm, but also that these complexes can be obtai ned by reduction of nitroalkanes. This is the first example of fully charac terized iron(II)-metabolite complexes of MP8. Such complexes constitute goo d models for those obtained upon oxidation of amphetamine or macrolids by c ytochromes P450. In addition, this is a new catalytic activity of MP8, whic h validates the use of this mini-enzyme as a convenient model for hemoprote ins of interest in toxicology and pharmacology such as cytochromes P450 and peroxidases. (C) 2000 Academic Press.