Uroporphyrinogen III synthase is an 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...

 involved in the metabolism

Metabolism

Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...

 of the cyclic tetrapyrrole

Tetrapyrrole

Tetrapyrroles are compounds containing four pyrrole rings. With the exception of corrin, the four pyrrole rings are interconnected through one-carbon bridges, in either a linear or a cyclic fashion...

 compound porphyrin

Porphyrin

Porphyrins are a group of organic compounds, many naturally occurring. One of the best-known porphyrins is heme, the pigment in red blood cells; heme is a cofactor of the protein hemoglobin. Porphyrins are heterocyclic macrocycles composed of four modified pyrrole subunits interconnected at...

. It is involved in the conversion of hydroxymethyl bilane into uroporphyrinogen III

Uroporphyrinogen III

Uroporphyrinogen III is an metabolic intermediate in the biosynthesis of protoporphyrin. It is created by the enzyme uroporphyrinogen III synthase, and is converted into coproporphyrinogen III by the enzyme uroporphyrinogen III decarboxylase.-See also:...

. This enzyme catalyses

Catalysis

Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....

 the inversion of the final pyrrole

Pyrrole

Pyrrole is a heterocyclic aromatic organic compound, a five-membered ring with the formula C4H4NH. It is a colourless volatile liquid that darkens readily upon exposure to air. Substituted derivatives are also called pyrroles, e.g., N-methylpyrrole, C4H4NCH3...

 unit (ring D) of the linear tetrapyrrole molecule, linking it to the first pyrrole unit (ring A), thereby generating a large macrocyclic structure, uroporphyrinogen III. The enzyme fold

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....

s into two alpha/beta domains

Protein domain

A protein domain is a part of protein sequence and structure that can evolve, function, and exist independently of the rest of the protein chain. Each domain forms a compact three-dimensional structure and often can be independently stable and folded. Many proteins consist of several structural...

 connected by a beta-ladder, the active site

Active site

In biology the active site is part of an enzyme where substrates bind and undergo a chemical reaction. The majority of enzymes are proteins but RNA enzymes called ribozymes also exist. The active site of an enzyme is usually found in a cleft or pocket that is lined by amino acid residues that...

 being located between the two domains.

Pathology

A deficiency is associated with Gunther's disease

Gunther's disease

Gunther disease, also known as congenital erythropoietic porphyria , uroporphyrinogen III synthase deficiency and UROS deficiency, is a congenital form of erythropoietic porphyria. It is a rare, autosomal recessive metabolic disorder affecting heme, caused by deficiency of the enzyme...

, also known as congenital erythropoietic porphyria (CEP). This is an autosomal recessive inborn error of metabolism that results from the markedly deficient activity of uroporphyrinogen III synthase .