Overview for MACiE Entry M0132
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 reduced flavin or flavoprotein as one donor, and incorporation of one atom of oxygen into the other donor)
Enzyme Name: alkanal monooxygenase (FMN-linked)
Biological Species: Vibrio harveyi (Bacteria)
Catalytic Chain UniprotKB Accession Codes:
- P07740 - Alkanal monooxygenase alpha chain
Representative PDB Code: 1luc - BACTERIAL LUCIFERASE (Resolution = 1.50 Å).
Catalytic CATH Codes:
"Other" CATH Codes:
Display structure information
Overall Comment: There are at least three alternative proposals for the decay of the FMN 4a-peroxyhemiacetal intermediate to emit light and yield the final products carboxylic acid FMN and water (Steps 4-7). A Baeyer-Villiger mechanism involving a hydride transfer from the intermediate. A mechanistic proposal involving a rate-limiting electron transfer to an intermediate dioxirane. And finally a modified version of the chemically initiated electron exchange luminescence which predicts that the oxidation potential of the flavin should affect the rate of bioluminescence reaction and found to be so in experiments with substituted FMN analogs . Mutational studies have shown that residues Phe46A Phe49A Phe114A Phe117A and Phe261A are critical to the luciferase activity due to the fact that their bulky and hydrophobic nature allow shielding of the critical intermediates from exposure to medium [3 6]. The torsional flexibility of Gly275A in a conserved loop has also been shown to be critical to luciferase activity .
The enzyme does not return to a state in which it can catalyse another reaction
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Stepwise Description of the Reaction
|Step 1||FMN undergoes a double bond rearrangement that results in the single electron transfer from FMN to dioxygen and a proton transfer from an unidentified base to the dioxygen molecule.|
|Step 2||The FMN and dioxygen radical species undergo a colligation reaction to form the FMN-peroxo adduct.|
|Step 3||The carbonyl carbon of the aldehyde substrate deprotonates the peroxo-intermediate, which attacks the carbonyl carbon of the aldehyde substrate in a nucleophilic addition.|
|Step 4||FMN donates a single electron into the peroxo group, causing a homolysis of the O-O bond.|
|Step 5||His44 deprotonates the intermediate, causing the C-H bond to homolyse, with a single electron being donates to the oxygen radical and one onto the carbon of the cleaved C-H bond.|
|Step 6||The bound oxygen on the FMN deprotonates His44. The negatively charged oxygen on the intermediate initiates a single electron transfer from the intermediate to the FMN which then emits a photon|
|Step 7||The FMN-bound hydroxyl group initiates an intramolecular elimination of water, generating the product FMN.|
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Catalytic Residues Involved
||Location of Function
- S. Huang et al. (1997), Biochemistry, 36, 14609-14615. Identification and characterization of a catalytic base in bacterial luciferase by chemical rescue of a dark mutant.
- S. Huang et al. (1998), Biochemistry, 37, 8614-8614. Identification and characterization of a catalytic base in bacterial luciferase by chemical rescue of a dark mutant (Addition/Correction).
- J. C. Low et al. (2002), Biochemistry, 41, 1724-1731. Functional roles of conserved residues in the unstructured loop of Vibrio harveyi bacterial luciferase.
- J. W. Eckstein et al. (1993), Biochemistry, 32, 404-411. Mechanism of bacterial bioluminescence: 4a,5-dihydroflavin analogs as models for luciferase hydroperoxide intermediates and the effect of substituents at the 8-position of flavin on luciferase kinetics.
- H. Li et al. (1999), Biochemistry, 38, 4409-4415. Effects of mutations of the alpha His45 residue of Vibrio harveyi luciferase on the yield and reactivity of the flavin peroxide intermediate.
- C.-H. Li et al. (2005), Biochemistry, 44, 12970-12977. Active site hydrophobicity is critical to the bioluminescence activity of Vibrio harveyi luciferase.
Homologue information for M0132 (1luc)
MACiE Homologues (within the PDB)
MACiE Homologues (within UniprotKB/SwissProt)
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