Cyclohexanone monooxygenase
| Cyclohexanone monooxygenase | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||
| EC no. | 1.14.13.22 | ||||||||
| CAS no. | 52037-90-8 | ||||||||
| Databases | |||||||||
| IntEnz | IntEnz view | ||||||||
| BRENDA | BRENDA entry | ||||||||
| ExPASy | NiceZyme view | ||||||||
| KEGG | KEGG entry | ||||||||
| MetaCyc | metabolic pathway | ||||||||
| PRIAM | profile | ||||||||
| PDB structures | RCSB PDB PDBe PDBsum | ||||||||
| |||||||||
Cyclohexanone monooxygenase (EC 1.14.13.22, cyclohexanone 1,2-monooxygenase, cyclohexanone oxygenase, cyclohexanone:NADPH:oxygen oxidoreductase (6-hydroxylating, 1,2-lactonizing)) is an enzyme with systematic name cyclohexanone,NADPH:oxygen oxidoreductase (lactone-forming).[1][2][3][4][5][6] This enzyme catalyses the following chemical reaction
- cyclohexanone + NADPH + H+ + O2 hexano-6-lactone + NADP+ + H2O
Cyclohexanone monooxygenase is a flavoprotein (FAD).
Enzyme Mechanism
Cyclohexanone monooxygenase (CHMO) uses NADPH and O2 as cosubstrates and FAD as a cofactor to insert an oxygen atom into the substrate. The process involves the formation of a falvin-peroxide and Criegee intermediate.[7]
CHMO is a member of the Baeyer-Villiger monooxygenase (BVMO) family and flavin-containing monooxygenases (FMO) superfamily.[7]
Cyclohexanone undergoes the following process, similar to the Baeyer-Villiger reactions, to be converted into hexano-6-lactone using CHMO.[8]
- NADPH attaches to the active site of CHMO and transfers a hydride resulting in FADH- and NADP+.
- A one-electron transfer from FADH- to O2 results in a superoxide radical and FAD semiquinone.
- Recombination of the radical pair results in the C4a-peroxyflavin intermediate.
- The C4a-peroxyflavin intermediate functions as a nucleophile and attacks the cyclohexanone substrate to form the Criegee intermediate.
- The intermediate undergoes a rearrangement to produce the hexano-6-lactone.
- CHMO releases H2O and NADP+ and regenerates FADH.
CHMO can also oxygenate cyclic ketones, aromatic aldehydes, and heteroatom-containing compounds. [9]
Enzyme Structure
Using CHMO isolated from Rhodococcus sp. Strain HI-31 and complexed with FAD and NADP+, two crystal structures were obtained showing CHMO in the open and closed conformations.[7] Structurally, CHMO is stable and contains 540 residues organized into a single subunit.
CHMO contains binding domains for NADP+ and FAD, which are connected by two unstructured loops. The NADP binding domain consists of the segments 152-208 and 335-380 with a helical domain constructed between residues 224-332. The helical domain shifts between the two dinucleotide (NADP+ and FAD) binding domains and helps form the substrate binding pocket. The FAD binding domain consists of the first 140 N-terminal residues as well as residues 387-540 from the C-terminus. [7]
The substrate binding pocket is well defined in the closed conformation and consists of the residues 145−146, 248, 279, 329, 434−435, 437, 492, and 507; FAD and NADP+ also contribute to the shape of the binding pocket.[7]
The key distinction between the open form, CHMOopen, and the closed form, CHMOclosed, lies in the conformation of residues 487-504, which form a loop. In the closed confirmation, the loop folds upon itself, internalizing the center portion of the loop. However, in the open conformation, the loop is not visible. It is predicted that this results from the loop adopting a solvent-exposed conformation.[7]
References
- ^ Donoghue NA, Norris DB, Trudgill PW (March 1976). "The purification and properties of cyclohexanone oxygenase from Nocardia globerula CL1 and Acinetobacter NCIB 9871". European Journal of Biochemistry. 63 (1): 175–92. doi:10.1111/j.1432-1033.1976.tb10220.x. PMID 1261545.
- ^ Sheng D, Ballou DP, Massey V (September 2001). "Mechanistic studies of cyclohexanone monooxygenase: chemical properties of intermediates involved in catalysis". Biochemistry. 40 (37): 11156–67. doi:10.1021/bi011153h. PMID 11551214.
- ^ Stewart, J.D. (1998). "Cyclohexanone monooxygenase: a useful reagent for asymmetric Baeyer-Villiger reactions". Curr. Org. Chem. 2: 195–216.
- ^ Kayser M, Mihovilovic M, Mrstik M, Martinez C, Stewart J (1999). "Asymmetric oxidations at sulfur catalyzed by engineered strains that overexpress cyclohexanone monooxygenase". New Journal of Chemistry. 23 (8): 827–832. doi:10.1039/a902283j.
- ^ Ottolina G, Bianchi S, Belloni B, Carrea G, Danieli B (1999). "First asymmetric oxidation of tertiary amines by cyclohexanone monooxygenase". Tetrahedron Lett. 40 (48): 8483–8486. doi:10.1016/s0040-4039(99)01780-3.
- ^ Colonna S, Gaggero N, Carrea G, Ottolina G, Pasta P, Zambianchi F (2002). "First asymmetric epoxidation catalysed by cyclohexanone monooxygenase". Tetrahedron Lett. 43 (10): 1797–1799. doi:10.1016/s0040-4039(02)00029-1.
- ^ a b c d e f Mirza, I. Ahmad; Yachnin, Brahm J.; Wang, Shaozhao; Grosse, Stephan; Bergeron, Hélène; Imura, Akihiro; Iwaki, Hiroaki; Hasegawa, Yoshie; Lau, Peter C. K.; Berghuis, Albert M. (2009-07-01). "Crystal Structures of Cyclohexanone Monooxygenase Reveal Complex Domain Movements and a Sliding Cofactor". Journal of the American Chemical Society. 131 (25): 8848–8854. doi:10.1021/ja9010578. ISSN 0002-7863.
- ^ Fordwour, Osei Boakye; Wolthers, Kirsten R. (2018-12-01). "Active site arginine controls the stereochemistry of hydride transfer in cyclohexanone monooxygenase". Archives of Biochemistry and Biophysics. 659: 47–56. doi:10.1016/j.abb.2018.09.025. ISSN 0003-9861.
- ^ Sheng, D.; Ballou, D. P.; Massey, V. (2001-09-18). "Mechanistic studies of cyclohexanone monooxygenase: chemical properties of intermediates involved in catalysis". Biochemistry. 40 (37): 11156–11167. doi:10.1021/bi011153h. ISSN 0006-2960. PMID 11551214.
External links
- Cyclohexanone+monooxygenase at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
