Cytochrome P450s are haem-thiolate proteins [6] involved in the oxidative degradation of various compounds. They are particularly well known for their role in the degradation of environmental toxins and mutagens. They can be divided into 4 classes, a ...
Cytochrome P450s are haem-thiolate proteins [6] involved in the oxidative degradation of various compounds. They are particularly well known for their role in the degradation of environmental toxins and mutagens. They can be divided into 4 classes, according to the method by which electrons from NAD(P)H are delivered to the catalytic site. Sequence conservation is relatively low within the family - there are only 3 absolutely conserved residues - but their general topography and structural fold are highly conserved. The conserved core is composed of a coil termed the 'meander', a four-helix bundle, helices J and K, and two sets of beta-sheets. These constitute the haem-binding loop (with an absolutely conserved cysteine that serves as the 5th ligand for the haem iron), the proton-transfer groove and the absolutely conserved EXXR motif in helix K. While prokaryotic P450s are soluble proteins, most eukaryotic P450s are associated with microsomal membranes. their general enzymatic function is to catalyse regiospecific and stereospecific oxidation of non-activated hydrocarbons at physiological temperatures [6].
Cytochrome P450 nitric oxide reductase (P450nor) is involved in a dissimilatory reduction of nitrite. Acts as a nitric oxide reductase. Is able to reduce nitrate and nitrite to a gaseous form of N2O when oxygen supply is limited or discontinued. May function as a detoxification mechanism.
This protein is found in denitrifying organisms such as Fusarium oxysporum. It is a member of the cytochrome P450 superfamily, which are heme-thiolate enzymes. There are two isoforms of P450nor in F. oxysporum, one of which uses NADH as cofactor exclusively, while the other uses NADH or NADPH.
P450nor catalyses the NAD(P)H-dependent reduction of two molecules of the free radical, nitric oxide (NO), to nitrous oxide (N2O). The reaction is unusual because it involves direct electron transfer, in the form of a hydride, from NAD(P)H to a redox protein (heme) that contains only a one-electron redox centre.
P450nor appears to have an important role in protecting the fungus from NO inhibition of mitochondria and other cellular damage that may result from the reaction of NO with other molecules such as oxygen or superoxide to form biologically hazardous compounds.
Defined by 4 residues: THR:A-243SER:A-286CYS:A-352ASP:A-393
