2.02015-09-08 17:50:06 -06002016-09-13 16:35:44 -0600ECMDB24213M2MDB0063304'-phosphopantetheine4'-phosphopantetheine is a metabolite in the pantothenate and coenzyme A biosynthesis pathway. It can be generated from pantatheine (via pantothenate kinase 1) or R-4'-phospho-pantothenoyl-L-cysteine (via phosphopantothenoylcysteine decarboxylase) or dephospho-CoA (via 4'-phosphopantetheine adenylyl-transferase and ectonucleotide pyrophosphatase). The conversion of 4'-phosphopantetheine (4'-PP) to dephospho-CoA, is catalyzed by 4'-phosphopantetheine adenylyl-transferase. It has been identified as an essential cofactor in in the biosynthesis of fatty acids, polyketides, depsipeptides, peptides, and compounds derived from both carboxylic and amino acid precursors. In particular it is a key prosthetic group of acyl carrier protein (ACP) and peptidyl carrier proteins (PCP) and aryl carrier proteins (ArCP) derived from Coenzyme A. Phosphopantetheine fulfils two demands. Firstly, the intermediates remain covalently linked to the synthases (or synthetases) in an energy-rich thiol ester linkage. Secondly, the flexibility and length of phosphopantetheine chain (approximately 2 nm) allows the covalently tethered intermediates to have access to spatially distinct enzyme active sites.2,3,3-trimethyl-4-(phosphonatooxy)-N-{2-[(2-sulfanylethyl)carbamoyl]ethyl}butanamide2,3,3-trimethyl-4-(phosphonatooxy)-N-{2-[(2-sulfanylethyl)carbamoyl]ethyl}butanamidelogp0.90logs-2.84solubility5.67e-01 g/llogp-0.4pka_strongest_acidic1.86pka_strongest_basic-0.91iupac2,3,3-trimethyl-4-(phosphonatooxy)-N-{2-[(2-sulfanylethyl)carbamoyl]ethyl}butanamidepolar_surface_area130.62refractivity82.57polarizability34.96rotatable_bond_count10acceptor_count5donor_count3physiological_charge-2formal_charge-2Pantothenate and CoA biosynthesisThe CoA biosynthesis requires compounds from two other pathways: aspartate metabolism and valine biosynthesis. It requires a Beta-Alanine and R-pantoate.
The compound (R)-pantoate is generated in two reactions, as shown by the interaction of alpha-ketoisovaleric acid, 5,10 methylene-THF and water through a 3-methyl-2-oxobutanoate hydroxymethyltransferase resulting in a tetrahydrofolic acid and a 2-dehydropantoate. This compound interacts with hydrogen through a NADPH driven acetohydroxy acid isomeroreductase resulting in the release of NADP and R-pantoate.
On the other hand L-aspartic acid interacts with a hydrogen ion and gets decarboxylated through an Aspartate 1- decarboxylase resulting in a carbon dioxide and a Beta-alanine.
Beta-alanine and R-pantoate interact with an ATP driven pantothenate synthetase resulting in pyrophosphate, AMP, hydrogen ion and pantothenic acid.
Pantothenic acid is phosphorylated through a ATP-driven pantothenate kinase resulting in a ADP, a hydrogen ion and D-4'-Phosphopantothenate. This compound interacts with a CTP and a L-cysteine resulting in a fused 4'-phosphopantothenoylcysteine decarboxylase and phosphopantothenoylcysteine synthetase resulting in a hydrogen ion, a pyrophosphate, a CMP and 4-phosphopantothenoylcysteine.
The latter compound interacts with a hydrogen ion through a fused 4'-phosphopantothenoylcysteine decarboxylase and phosphopantothenoylcysteine synthetase resulting in a carbon dioxide release and a 4-phosphopantetheine. This compound interacts with an ATP, hydrogen ion and an phosphopantetheine adenylyltransferase resulting in a release of pyrophosphate, and dephospho-CoA.
Dephospho-CoA reacts with an ATP driven dephospho-CoA kinase resulting in a ADP , a hydrogen ion and a Coenzyme A.
. The latter is converted into (R)-4'-phosphopantothenate is two steps, involving a β-alanine ligase and a kinase. In most organsims the ligase acts before the kinase (EC 6.3.2.1, pantoate—β-alanine ligase (AMP-forming) followed by EC 2.7.1.33, pantothenate kinase, as described in phosphopantothenate biosynthesis I and phosphopantothenate biosynthesis II. However, in archaea the order is reversed, and EC 2.7.1.169, pantoate kinase acts before EC 6.3.2.36, 4-phosphopantoate—β-alanine ligase, as described in phosphopantothenate biosynthesis III.
The kinases are feedback inhibited by CoA itself, accounting for the primary regulatory mechanism of CoA biosynthesis. The addition of L-cysteine to (R)-4'-phosphopantothenate, resulting in the formation of R-4'-phosphopantothenoyl-L-cysteine (PPC), is followed by decarboxylation of PPC to 4'-phosphopantetheine. The ultimate reaction is catalyzed by EC 2.7.1.24, dephospho-CoA kinase, which converts 4'-phosphopantetheine to CoA. All enzymes of this pathway are essential for growth.
The reactions in the biosynthetic route towards CoA are identical in most organisms, although there are differences in the functionality of the involved enzymes. In plants every step is catalyzed by single monofunctional enzymes, whereas in bacteria and mammals bifunctional enzymes are often employed [Rubio06].PW000828ec00770MetabolicCitrate lyase activationThe citrate lyase activation starts with a 3-dephospho-CoA reacting with ATP and a hydrogen ion through a triphosphoribosyl-dephospho-CoA synthase resulting in a adenine and a 2'-(5'-triphospho-alpha-D-ribosyl)-3'-dephospho-CoA. The latter compound in turn reacts with with a citrate lyase acyl-carrier protein through a apo-citrate lyase phosphoribosyl-dephospho-CoA transferase resulting in the release of a pyrophosphate and a hydrogen ion and a holo citrate lyase acyl-carrier protein.This protein complex can either react with a hydrogen ion and a acetate resulting in the release of a water and an acetyl-holo citrate lyase acyl-carrier protein.
The holo acyl-carrier protein creacts with an ATP and an acetate through a citrate lyase synthase resulting in the release of an AMP, a pyrophosphate and an acetyl-holo citrate lyase acyl-ccarrier protein.
The holo citrate lyase acyl-carrier protein can also interact with an S-acetyl phosphopantethiene resulting in the release of a 4-phosphopantethiene and an acetyl-holo citrate lyase acyl-carrier protein.PW002075MetabolicSpecdb::MsMs28760Specdb::MsMs28761Specdb::MsMs28762Specdb::MsMs35318Specdb::MsMs35319Specdb::MsMs35320Phosphopantetheine adenylyltransferaseP0A6I6COAD_ECOLIcoaDhttp://ecmdb.ca/proteins/P0A6I6.xmlCoenzyme A biosynthesis bifunctional protein coaBCP0ABQ0COABC_ECOLIcoaBChttp://ecmdb.ca/proteins/P0ABQ0.xml4-Phosphopantothenoylcysteine + Hydrogen ion > Carbon dioxide + 4'-phosphopantetheine + 4'-phosphopantetheinePW_R0030054'-phosphopantetheine + Adenosine triphosphate + Hydrogen ion + 4'-phosphopantetheine > Pyrophosphate + Dephospho-CoAPW_R003004