Malonyl-CoA is a
coenzyme ACoenzyme A 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...
derivative.
It plays a key role in chain elongation in
fatty acidIn chemistry, especially biochemistry, a fatty acid is a carboxylic acid often with a long unbranched aliphatic tail , which is either saturated or unsaturated...
biosynthesis and
polyketidePolyketides are secondary metabolites from bacteria, fungi, plants, and animals. Polyketides are biosynthesized by the polymerization of acetyl and propionyl subunits in a similar process to fatty acid synthesis...
biosynthesis.
Malonyl-CoA is also used in transporting alpha-ketoglutarate across the mitochondrial membrane into the mitochondrial matrix.
In the former, it provides 2-carbon units to fatty acids and commits them to fatty acid chain synthesis.
Malonyl-CoA is formed by carboxylating
acetyl-CoAAcetyl-CoA is an important molecule in metabolism, used in many biochemical reactions. Its main use is to convey the carbon atoms within the acetyl group to the citric acid cycle to be oxidized for energy production. In chemical structure, acetyl-CoA is the thioester between coenzyme A and acetic...
using the enzyme
acetyl-CoA carboxylaseAcetyl-CoA carboxylase is a biotin-dependent enzyme that catalyzes the irreversible carboxylation of acetyl-CoA to produce malonyl-CoA through its two catalytic activities, biotin carboxylase and carboxyltransferase...
.
Malonyl-CoA is a
coenzyme ACoenzyme A 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...
derivative.
Functions
It plays a key role in chain elongation in
fatty acidIn chemistry, especially biochemistry, a fatty acid is a carboxylic acid often with a long unbranched aliphatic tail , which is either saturated or unsaturated...
biosynthesis and
polyketidePolyketides are secondary metabolites from bacteria, fungi, plants, and animals. Polyketides are biosynthesized by the polymerization of acetyl and propionyl subunits in a similar process to fatty acid synthesis...
biosynthesis.
Malonyl-CoA is also used in transporting alpha-ketoglutarate across the mitochondrial membrane into the mitochondrial matrix.
Fatty acid biosynthesis
In the former, it provides 2-carbon units to fatty acids and commits them to fatty acid chain synthesis.
Malonyl-CoA is formed by carboxylating
acetyl-CoAAcetyl-CoA is an important molecule in metabolism, used in many biochemical reactions. Its main use is to convey the carbon atoms within the acetyl group to the citric acid cycle to be oxidized for energy production. In chemical structure, acetyl-CoA is the thioester between coenzyme A and acetic...
using the enzyme
acetyl-CoA carboxylaseAcetyl-CoA carboxylase is a biotin-dependent enzyme that catalyzes the irreversible carboxylation of acetyl-CoA to produce malonyl-CoA through its two catalytic activities, biotin carboxylase and carboxyltransferase...
. One molecule of acetyl-CoA joins with a molecule of
carbon dioxideCarbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state...
, requiring energy rendered from
ATPAdenosine-5'-triphosphate is a multifunctional nucleotide that plays an important role in cell biology as a coenzyme, that is, the "molecular unit of currency" of intracellular energy transfer. ATP transports chemical energy within cells for metabolism...
.
Malonyl-CoA is utilised in fatty acid biosynthesis by the enzyme
malonyl coenzyme A:acyl carrier proteinThe acyl carrier protein is an important component in both fatty acid and polyketide biosynthesis with the growing chain bound during synthesis as a thiol ester at the distal thiol of a 4'-phosphopantethiene moiety...
transacylase (MCAT). MCAT serves to transfer
malonateThe malonate or propanedioate ion is CH222− . Malonate compounds include salts and esters of malonic acid, such as...
from malonyl-CoA to the terminal
thiolIn organic chemistry, a thiol is a compound that contains the functional group composed of a sulfur-hydrogen bond . Being the sulfur analogue of an alcohol group , this functional group is referred to either as a thiol group or a sulfhydryl group...
of
holo-
acyl carrier proteinThe acyl carrier protein is an important component in both fatty acid and polyketide biosynthesis with the growing chain bound during synthesis as a thiol ester at the distal thiol of a 4'-phosphopantethiene moiety...
(ACP).
Polyketide biosynthesis
Controversy still exists as to whether MCAT is also involved in bacterial
polyketidePolyketides are secondary metabolites from bacteria, fungi, plants, and animals. Polyketides are biosynthesized by the polymerization of acetyl and propionyl subunits in a similar process to fatty acid synthesis...
biosynthesis; however, there is evidence that the acyl carrier protein from a variety of bacterial polyketide synthases is capable of self-malonylation in the presence of malonyl-CoA.
Regulation
Malonyl-CoA is a highly-regulated molecule in fatty acid synthesis; as such, it inhibits the rate-limiting step in beta-oxidation of fatty acids. Malonyl CoA inhibits fatty acids from associating with
carnitineCarnitine is a quaternary ammonium compound biosynthesized from the amino acids lysine and methionine. In living cells, it is required for the transport of fatty acids from the cytosol into the mitochondria during the breakdown of lipids for the generation of metabolic energy. It is often sold as...
, thereby preventing them from entering the mitochondria where fatty acid oxidation and degradation occur.
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