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Overview for MACiE Entry M0136

Version history

General Information

EC Number: 1.14.19.2 (A member of the Oxidoreductases, Acting on paired donors, with O2 as oxidant and incorporation or reduction of oxygen. The oxygen incorporated need not be derived from O2, With oxidation of a pair of donors resulting in the reduction of O2 to two molecules of water)

Enzyme Name: acyl-[acyl-carrier-protein] desaturase

Biological Species: Ricinus communis (Castor bean)

Catalytic Chain UniprotKB Accession Codes:

  • P22337 - Acyl-[acyl-carrier-protein] desaturase, chloroplastic

Representative PDB Code: 1afr - STEAROYL-ACYL CARRIER PROTEIN DESATURASE FROM CASTOR SEEDS (Resolution = 2.40 Å).

Catalytic CATH Codes:

Display structure information

Overall Reaction:

Image of oxygen

Image of proton

Image of reduced ferredoxin

Image of stearoyl-[acyl-carrier protein]

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Image of oxidised ferredoxin

Image of oleoyl-[acyl-carrier protein]

Image of water

oxygen
C00007
CHEBI:15379
2 proton
C00080
CHEBI:24636
reduced ferredoxin
C00138
CHEBI:17513
stearoyl-[acyl-carrier protein]
C04088
oxidised ferredoxin
C00139
CHEBI:17908
oleoyl-[acyl-carrier protein]
C01203
2 water
C00001
CHEBI:15377

This reaction is irreversible.


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Stepwise Description of the Reaction

Step 1Ferredoxin donates a single electron, through Trp62, Asp228 and His146, to one of the Fe(III) centres.
Step 2Ferredoxin donates a second single electron, through Trp62, Asp228 and His146, to the second Fe(III) centre, which initiates the loss of the bridging O2- ion. This oxygen atom is displaced by dioxygen.
Step 3Water coordinates to one of the Fe(II) centres, which causes the centre to donate a single electron to the dioxide molecule, initiating the first of two homolytic additions of the dioxygen molecule to both Fe(II) centres and the second Fe(II) centre also donates a single electron to the dioxygen bridge.
Step 4Both Fe(III) centres donate a single electron to the bridging dioxygen, cleaving the O-O bond and initiating one of the oxygen atoms to deprotonates the bound water and regenerating the oxo-bridge.
Step 5The hydroxide on the first Fe(IV) centre deprotonates the stearoyl-[acyl-carrier protein] substrate, initiating the elimination of a hydride ion, which attacks the second Fe(IV) bound hydroxide. The excess electrons are donated singly to both Fe(IV) centres, regenerating the enzyme.

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Catalytic Residues Involved

Type Number Chain Location of Function
Trp 62 A Side Chain
His 146 A Side Chain
Thr 199 A Side Chain
Asp 228 A Side Chain

Metal Cofactors for M0136

Type Het group Number Chain
iron FE2 364 x Overview
iron FE2 365 x Overview

References

  1. B. G. Fox et al. (2004), Acc. Chem. Res., 37, 421-429. Reactions of the diiron enzyme stearoyl-acyl carrier protein desaturase.
    Medline: 15260504
  2. Y. Lindqvist et al. (1996), The EMBO Journal, 15, 4081-4092. Crystal structure of delta9 stearoyl-acyl carrier protein desaturase from castor seed and its relationship to other di-iron proteins.
    Medline: 8861937
  3. P. Nordlund et al. (1993), J. Mol. Biol., 232, 123-164. Structure and function of the Escherichia coli ribonucleotide reductase protein R2.
    Medline: 8331655

Homologue information for M0136 (1afr)

CSA Homologues

MACiE Homologues (within the PDB)

MACiE Homologues (within UniprotKB/SwissProt)


Links to this entry in other databases

Link to EC-PDB-SUM Link to PDB-SUM Link to RCSB PDB Link to PDBe Link to CSA
Link to MetaCyc Link to KEGG Link to BRENDA Link to ExplorENZ
Link to EzCatDB

GOA logo
fatty acid metabolic process (biological process)
fatty acid biosynthetic process (biological process)
lipid biosynthetic process (biological process)
chloroplast (cellular component)
plastid (cellular component)
oxidoreductase activity (molecular function)
acyl-[acyl-carrier-protein] desaturase activity (molecular function)
transition metal ion binding (molecular function)
oxidation-reduction process (biological process)
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