Phosphogluconate dehydrogenase 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...

 in the pentose phosphate pathway

Pentose phosphate pathway

The pentose phosphate pathway is a process that generates NADPH and pentoses . There are two distinct phases in the pathway. The first is the oxidative phase, in which NADPH is generated, and the second is the non-oxidative synthesis of 5-carbon sugars...

. It forms ribulose 5-phosphate

Ribulose 5-phosphate

Ribulose 5-phosphate is one of the end-products of the pentose phosphate pathway. It is also an intermediate in the Calvin cycle.It is formed by phosphogluconate dehydrogenase, and it can be acted upon by phosphopentose isomerase and phosphopentose epimerase....

 from 6-phosphogluconate

6-Phosphogluconate

6-Phosphogluconic acid is an intermediate in the pentose phosphate pathway and the Entner–Doudoroff pathway.It is formed by 6-phosphogluconolactonase, and acted upon by phosphogluconate dehydrogenase to produce ribulose 5-phosphate. It may also be acted upon by 6-phosphogluconate dehydratase to...

.

It is an oxidative carboxylase that 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 decarboxylating reduction

Redox

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

 of 6-phosphogluconate

6-Phosphogluconate

6-Phosphogluconic acid is an intermediate in the pentose phosphate pathway and the Entner–Doudoroff pathway.It is formed by 6-phosphogluconolactonase, and acted upon by phosphogluconate dehydrogenase to produce ribulose 5-phosphate. It may also be acted upon by 6-phosphogluconate dehydratase to...

 into ribulose 5-phosphate

Ribulose 5-phosphate

Ribulose 5-phosphate is one of the end-products of the pentose phosphate pathway. It is also an intermediate in the Calvin cycle.It is formed by phosphogluconate dehydrogenase, and it can be acted upon by phosphopentose isomerase and phosphopentose epimerase....

 in the presence of NADP. This reaction is a component of the hexose

Hexose

In organic chemistry, a hexose is a monosaccharide with six carbon atoms, having the chemical formula C6H12O6. Hexoses are classified by functional group, with aldohexoses having an aldehyde at position 1, and ketohexoses having a ketone at position 2....

 mono-phosphate shunt and pentose phosphate pathway

Pentose phosphate pathway

The pentose phosphate pathway is a process that generates NADPH and pentoses . There are two distinct phases in the pathway. The first is the oxidative phase, in which NADPH is generated, and the second is the non-oxidative synthesis of 5-carbon sugars...

s (PPP). Prokaryotic and eukaryotic 6PGD are 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...

s of about 470 amino acid

Amino acid

Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...

s whose sequence

Sequence (biology)

A sequence in biology is the one-dimensional ordering of monomers, covalently linked within in a biopolymer; it is also referred to as the primary structure of the biological macromolecule.-See also:* Protein sequence* DNA sequence...

s are highly conserved. The protein is a homodimer in which the monomer

Monomer

A monomer is an atom or a small molecule that may bind chemically to other monomers to form a polymer; the term "monomeric protein" may also be used to describe one of the proteins making up a multiprotein complex...

s act independently : each contains a large, mainly alpha-helical

Alpha helix

A common motif in the secondary structure of proteins, the alpha helix is a right-handed coiled or spiral conformation, in which every backbone N-H group donates a hydrogen bond to the backbone C=O group of the amino acid four residues earlier...

 domain

Domain (biology)

In biological taxonomy, a domain is the highest taxonomic rank of organisms, higher than a kingdom. According to the three-domain system of Carl Woese, introduced in 1990, the Tree of Life consists of three domains: Archaea, Bacteria and Eukarya...

 and a smaller beta-alpha-beta domain, containing a mixed parallel and anti-parallel 6-stranded beta sheet

Beta sheet

The β sheet is the second form of regular secondary structure in proteins, only somewhat less common than the alpha helix. Beta sheets consist of beta strands connected laterally by at least two or three backbone hydrogen bonds, forming a generally twisted, pleated sheet...

. NADP is bound in a cleft in the small domain, the substrate binding

Binding (molecular)

Molecular binding is an attractive interaction between two molecules which results in a stable association in which the molecules are in close proximity to each other...

in an adjacent pocket.