Cytochromes P450 (CYPs), nitric oxide synthases (NOS )and methane monooxigenase, (MMO) are powerful enzyme hydroxylation systems of organic substrates (CYPs) and nitricoxide synthesis (NOS ). Despite the huge diversity of substrates, catalysis is carried out by a single fundamental mechanism. The mechanism includes the following key stages:activation of molecular oxygen by a two-molecular mechanism, decomposition of the product into a radical-like particle that attacks the substrate.