The flavin-containing monooxygenase (FMO) protein

Protein

Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

 family consists of a group of enzyme

Enzyme

Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

s that catalyze chemical reactions via the bound cofactor

Cofactor (biochemistry)

A cofactor is a non-protein chemical compound that is bound to a protein and is required for the protein's biological activity. These proteins are commonly enzymes, and cofactors can be considered "helper molecules" that assist in biochemical transformations....

 flavin. These reactions involve oxidation

Redox

Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....

 of heteroatom

Heteroatom

In organic chemistry, a heteroatom is any atom that is not carbon or hydrogen. Usually, the term is used to indicate that non-carbon atoms have replaced carbon in the backbone of the molecular structure...

s, particularly nucleophilic

Nucleophile

A nucleophile is a species that donates an electron-pair to an electrophile to form a chemical bond in a reaction. All molecules or ions with a free pair of electrons can act as nucleophiles. Because nucleophiles donate electrons, they are by definition Lewis bases.Nucleophilic describes the...

 atoms such as the nitrogen

Nitrogen

Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

 of amine

Amine

Amines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group. Important amines include amino acids, biogenic amines,...

s.

These enzymes metabolise xenobiotics. Using an NADPH cofactor and FAD prosthetic group, these microsomal proteins catalyse the oxygenation of nucleophilic nitrogen, sulphur, phosphorus and selenium atoms in a range of structurally diverse compounds. FMOs have been implicated in the metabolism of a number of pharmaceuticals, pesticides and toxicants. In man, lack of hepatic FMO-catalysed trimethylamine metabolism results in trimethylaminuria (fish odour syndrome). Five mammalian forms of FMO are now known and have been designated FMO1-FMO5.

The best-known such protein is called FMO3 and is mutated

Mutation

In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...

 in the vast majority of cases of trimethylaminuria

Trimethylaminuria

Trimethylaminuria , also known as fish odor syndrome or fish malodor syndrome, is a rare metabolic disorder that causes a defect in the normal production of the enzyme Flavin containing monooxygenase 3...

, a genetic disease that causes deficiencies in breakdown of trimethylamine

Trimethylamine

Trimethylamine is an organic compound with the formula N3. This colorless, hygroscopic, and flammable tertiary amine has a strong "fishy" odor in low concentrations and an ammonia-like odor at higher concentrations...

 and gives the patient a fishy body odor. In yeast

Yeast

Yeasts are eukaryotic micro-organisms classified in the kingdom Fungi, with 1,500 species currently described estimated to be only 1% of all fungal species. Most reproduce asexually by mitosis, and many do so by an asymmetric division process called budding...

, FMO proteins are associated with redox cycling of glutathione

Glutathione

Glutathione is a tripeptide that contains an unusual peptide linkage between the amine group of cysteine and the carboxyl group of the glutamate side-chain...

 to glutathione disulfide

Glutathione disulfide

Glutathione disulfide is a disulfide derived from two glutathione molecules.In living cells, glutathione disulfide is reduced into two molecules of glutathione with reducing equivalents from the coenzyme NADPH. This reaction is catalyzed by the enzyme glutathione reductase...

, a system that maintains the redox state of the cell and heavily influences the protein folding

Protein folding

Protein folding is the process by which a protein structure assumes its functional shape or conformation. It is the physical process by which a polypeptide folds into its characteristic and functional three-dimensional structure from random coil....

 rates of disulfide bond

Disulfide bond

In chemistry, a disulfide bond is a covalent bond, usually derived by the coupling of two thiol groups. The linkage is also called an SS-bond or disulfide bridge. The overall connectivity is therefore R-S-S-R. The terminology is widely used in biochemistry...

-containing proteins.