Overview for MACiE Entry M0136
EC Number: 220.127.116.11 (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:
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This reaction is irreversible.
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Stepwise Description of the Reaction
|Step 1||Ferredoxin donates a single electron, through Trp62, Asp228 and His146, to one of the Fe(III) centres.|
|Step 2||Ferredoxin 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 3||Water 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 4||Both 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 5||The 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
||Location of Function
Metal Cofactors for M0136
- B. G. Fox et al. (2004), Acc. Chem. Res., 37, 421-429. Reactions of the diiron enzyme stearoyl-acyl carrier protein desaturase.
- 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.
- P. Nordlund et al. (1993), J. Mol. Biol., 232, 123-164. Structure and function of the Escherichia coli ribonucleotide reductase protein R2.
Homologue information for M0136 (1afr)
MACiE Homologues (within the PDB)
MACiE Homologues (within UniprotKB/SwissProt)
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