Malonyl-CoA
Encyclopedia
Malonyl-CoA is a coenzyme A
derivative.
biosynthesis and polyketide
biosynthesis.
Malonyl-CoA is also used in transporting alpha-ketoglutarate across the mitochondrial membrane into the mitochondrial matrix.
Malonyl-CoA is formed by carboxylating acetyl-CoA
using the enzyme acetyl-CoA carboxylase
. One molecule of acetyl-CoA joins with a molecule of bicarbonate
, requiring energy rendered from ATP
.
Malonyl-CoA is utilised in fatty acid biosynthesis by the enzyme malonyl coenzyme A:acyl carrier protein
transacylase (MCAT). MCAT serves to transfer malonate
from malonyl-CoA to the terminal thiol
of holo-acyl carrier protein
(ACP).
biosynthesis. The fatty acid MCAT together with an acyl carrier protein (ACP), and a polyketide synthase and chain-length factor heterodimer, constitutes the minimal PKS of type II polyketides.
by regulating the enzyme carnitine acyltransferase, thereby preventing them from entering the mitochondria where fatty acid oxidation and degradation occur.
Coenzyme A
Coenzyme 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. All sequenced genomes encode enzymes that use coenzyme A as a substrate, and around 4% of cellular enzymes use it as a substrate...
derivative.
Functions
It plays a key role in chain elongation in fatty acidFatty acid
In chemistry, especially biochemistry, a fatty acid is a carboxylic acid with a long unbranched aliphatic tail , which is either saturated or unsaturated. Most naturally occurring fatty acids have a chain of an even number of carbon atoms, from 4 to 28. Fatty acids are usually derived from...
biosynthesis and polyketide
Polyketide
Polyketides are secondary metabolites from bacteria, fungi, plants, and animals. Polyketides are usually biosynthesized through the decarboxylative condensation of malonyl-CoA derived extender units 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-CoA
Acetyl-CoA
Acetyl coenzyme A or acetyl-CoA is an important molecule in metabolism, used in many biochemical reactions. Its main function 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...
using the enzyme acetyl-CoA carboxylase
Acetyl-CoA carboxylase
Acetyl-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 bicarbonate
Bicarbonate
In inorganic chemistry, bicarbonate is an intermediate form in the deprotonation of carbonic acid...
, requiring energy rendered from ATP
Adenosine triphosphate
Adenosine-5'-triphosphate is a multifunctional nucleoside triphosphate used in cells as a coenzyme. It is often called 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 protein
Acyl carrier protein
The 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 malonate
Malonate
The malonate or propanedioate ion is CH222− . Malonate compounds include salts and esters of malonic acid, such as*diethyl malonate, 2,*dimethyl malonate, 2,...
from malonyl-CoA to the terminal thiol
Thiol
In organic chemistry, a thiol is an organosulfur compound that contains a carbon-bonded sulfhydryl group...
of holo-acyl carrier protein
Acyl carrier protein
The 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
There is little controversy about the fact that MCAT is also involved in bacterial polyketidePolyketide
Polyketides are secondary metabolites from bacteria, fungi, plants, and animals. Polyketides are usually biosynthesized through the decarboxylative condensation of malonyl-CoA derived extender units in a similar process to fatty acid synthesis...
biosynthesis. The fatty acid MCAT together with an acyl carrier protein (ACP), and a polyketide synthase and chain-length factor heterodimer, constitutes the minimal PKS of type II polyketides.
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
Carnitine 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 widely...
by regulating the enzyme carnitine acyltransferase, thereby preventing them from entering the mitochondria where fatty acid oxidation and degradation occur.