In enzymology and

molecular biology Molecular biology is the branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including biomolecular synthesis, modification, mechanisms, and interactions. The study of chemical and phys ...

, a holo- cyl-carrier-proteinsynthase (ACPS, ) is an

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different molecule ...

that

catalyzes Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

the chemical reaction: :CoA- '-phosphopantetheine+ apo- acyl carrier protein

\rightleftharpoons

adenosine 3',5'-bisphosphate + holo- acyl carrier protein This enzyme belongs to the family of

transferase A transferase is any one of a class of enzymes that catalyse the transfer of specific functional groups (e.g. a methyl or glycosyl group) from one molecule (called the donor) to another (called the acceptor). They are involved in hundreds of ...

s, specifically those transferring non-standard substituted phosphate groups. It is also known as 4'-phosphopantetheinyl transferase after the group it transfers.

Function

All ACPS enzymes known so far are evolutionally related to each other in a single superfamily of

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respon ...

s. It transfers a 4'- phosphopantetheine (4'-PP) moiety from

coenzyme A Coenzyme A (CoA, SHCoA, CoASH) is a coenzyme, notable for its role in the synthesis and oxidation of fatty acids, and the oxidation of pyruvate in the citric acid cycle. All genomes sequenced to date encode enzymes that use coenzyme A as a subs ...

(CoA) to an invariant

serine Serine (symbol Ser or S) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α- amino group (which is in the protonated − form under biological conditions), a carboxyl group (which is in the deprotonated − for ...

in an acyl carrier protein (ACP), a small protein responsible for acyl group activation in

fatty acid In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, ...

biosynthesis. This

post-translational modification Post-translational modification (PTM) is the covalent and generally enzymatic modification of proteins following protein biosynthesis. This process occurs in the endoplasmic reticulum and the golgi apparatus. Proteins are synthesized by ribos ...

renders holo-ACP capable of

acyl In chemistry, an acyl group is a moiety derived by the removal of one or more hydroxyl groups from an oxoacid, including inorganic acids. It contains a double-bonded oxygen atom and an alkyl group (). In organic chemistry, the acyl group ( I ...

group activation via thioesterification of the cysteamine

thiol In organic chemistry, a thiol (; ), or thiol derivative, is any organosulfur compound of the form , where R represents an alkyl or other organic substituent. The functional group itself is referred to as either a thiol group or a sulfhydryl gro ...

of 4'-PP. This superfamily consists of two subtypes: the trimeric ACPS type such as '' E. coli'' ACPS and the monomeric Sfp (PCP-synthesizing) type such as '' B. subtilis'' SFP. Structures from both families are now known. The active site accommodates a

magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ...

ion. The most highly conserved regions of the protein are involved in binding the

ion.

Nomenclature

The

systematic name A systematic name is a name given in a systematic way to one unique group, organism, object or chemical substance, out of a specific population or collection. Systematic names are usually part of a nomenclature. A semisystematic name or semitrivial ...

of this enzyme class is CoA- '-phosphopantetheineapo- cyl-carrier-protein4'-pantetheinephosphotransferase. Other names in common use, disregarding the synthetase/synthase spelling difference, include acyl carrier protein holoprotein synthetase, holo-ACP synthetase, coenzyme A:fatty acid synthetase apoenzyme 4'-phosphopantetheine, acyl carrier protein synthetase (ACPS), PPTase, acyl carrier protein synthase, P-pant transferase, and CoA:apo- cyl-carrier-proteinpantetheinephosphotransferase.

Structural studies

As of late 2007, 8 structures have been solved for this class of enzymes, with PDB accession codes , , , , , , , and .

Function

Nomenclature

Structural studies

References

Further reading