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Search The CSA
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Catalytic Site Atlas

CSA LITERATURE entry for 1mvn

E.C. namephosphopantothenoylcysteine decarboxylase
SpeciesArabidopsis thaliana (Thale cress)
E.C. Number (IntEnz) 4.1.1.36
CSA Homologues of 1mvn1e20,1g63,1mvl,
CSA Entries With UniProtID Q9SWE5
CSA Entries With EC Number 4.1.1.36
PDBe Entry 1mvn
PDBSum Entry 1mvn
MACiE Entry 1mvn

Literature Report

IntroductionThe Arabidopsis thaliana flavoprotein AtHAL3a catalyses the oxidative decarboxylation of 4'-phosphopantothenoylcysteine to 4'-phosphopantetheine, a step in coenzyme A biosynthesis. It belongs to the family of homo-oligomeric flavin-containing cysteine decarboxylases (HFCD) family.
MechansimThe mechanism involves 2 reaction steps:oxidative decarboxylation to form a thioaldehyde intermediate and the reduction of the intermediate. First, a thiolate ion is stabilised by His90, which acts as a base to deprotonate the thio-group of the substrate cysteine. Electrons are transferred by an SET mechanism from the thiolate to FMN together with the deprotonation of the beta-carbon of the substrate cysteine by His90. This results in a thioaldehyde intermediate which decarboxylates spontaneously, forming a cis ene-thiolate. The ene-thiolate is then reduced by direct hydride transfer from FMNH2 to the beta-carbon atom and the concomitant protonation of the alpha-carbon by Cys175.
Reaction

Catalytic Sites for 1mvn

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
SerA175175macie:sideChainIt acts as an acid to deprotonate the alpha-carbon atom in the cis ene-thiolate intermediate, concomitant to the hydride transfer from FMNH2 to the beta-carbon atom, in the reduction of the intermediate.
HisA9090macie:sideChainIt acts as a base to deprotonate the thio-group of the substrate cysteine to form a thiolate ion.

Literature References

Notes:
Kupke T
Arabidopsis thaliana flavoprotein AtHAL3a catalyzes the decarboxylation of 4'-Phosphopantothenoylcysteine to 4'-phosphopantetheine, a key step in coenzyme A biosynthesis.
J Biol Chem 2001 276 19190-19196
PubMed: 11279129
Steinbacher S
Crystal structure of the plant PPC decarboxylase AtHAL3a complexed with an ene-thiol reaction intermediate.
J Mol Biol 2003 327 193-202
PubMed: 12614618
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