Nitrile hydratase: Difference between revisions
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==Metabolic pathway== |
==Metabolic pathway== |
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Nitrile hydratase and amidase are the two hydrolytic enzymes responsible for the sequential metabolism of [[nitriles]] in some bacteria and fungi that are capable of utilising aliphatic nitriles as the sole source of nitrogen and carbon. A sequence has been identified in genome of the eukaryote Monosiga brevicollis which has been suggested to encode for a nitrile hydratase.<ref>Foerstner KU, Doerks T, Muller J, Raes J, Bork P |
Nitrile hydratase and amidase are the two hydrolytic enzymes responsible for the sequential metabolism of [[nitriles]] in some bacteria and fungi that are capable of utilising aliphatic nitriles as the sole source of nitrogen and carbon. A sequence has been identified in genome of the eukaryote Monosiga brevicollis which has been suggested to encode for a nitrile hydratase.<ref name="pmid19096720">{{cite journal | author = Foerstner KU, Doerks T, Muller J, Raes J, Bork P | title = A nitrile hydratase in the eukaryote Monosiga brevicollis | journal = PLoS ONE | volume = 3 | issue = 12 | pages = e3976 | year = 2008 | pmid = 19096720 | pmc = 2603476 | doi = 10.1371/journal.pone.0003976 | url = | issn = }}</ref> |
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==Industrial applications== |
==Industrial applications== |
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Revision as of 07:15, 18 October 2009
| nitrile hydratase | |||||||||
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| Identifiers | |||||||||
| EC no. | 4.2.1.84 | ||||||||
| CAS no. | 82391-37-5 | ||||||||
| Databases | |||||||||
| IntEnz | IntEnz view | ||||||||
| BRENDA | BRENDA entry | ||||||||
| ExPASy | NiceZyme view | ||||||||
| KEGG | KEGG entry | ||||||||
| MetaCyc | metabolic pathway | ||||||||
| PRIAM | profile | ||||||||
| PDB structures | RCSB PDB PDBe PDBsum | ||||||||
| Gene Ontology | AmiGO / QuickGO | ||||||||
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In enzymology, nitrile hydratases (NHases; EC 4.2.1.84) are mononuclear iron or non-corrinoid cobalt enzymes that catalyse the hydration of diverse nitriles to their corresponding amides
R-C≡N + H2O → R-C(O)NH2
Metal cofactor
Cobalt is a toxic compound for humans and most organisms. In biochemistry, cobalt is generally found only in a corrin ring, such as vitamin B12. Nitrile hydratase is one of the rare enzymes that use cobalt directly as a cofactor. The mechanism by which the cobalt is transported to NHase without causing toxicity is unclear, although a cobalt permease has been identified, which transports cobalt across the cell membrane. The identity of the metal in the active site of a nitrile hydratase can be predicted by analysis of the sequence data of the alpha subunit in the region where the metal is bound. The presence of the amino acid sequence VCTLC indicates a Co-centred NHase and the presence of VCSLC indicates Fe-centred NHase.
Metabolic pathway
Nitrile hydratase and amidase are the two hydrolytic enzymes responsible for the sequential metabolism of nitriles in some bacteria and fungi that are capable of utilising aliphatic nitriles as the sole source of nitrogen and carbon. A sequence has been identified in genome of the eukaryote Monosiga brevicollis which has been suggested to encode for a nitrile hydratase.[1]
Industrial applications
NHases have been efficiently used for the industrial production of acrylamide from acrylonitrile and for removal of nitriles from wastewater. Photosensitive NHases intrinsically possess nitric oxide (NO) bound to the iron centre and its photodissociation activates the enzyme.
Structure
NHases are composed of two types of subunits, α and β, which are not related in amino acid sequence. NHases exist as αβ dimers or α2β2 tetramers and bind one metal atom per αβ unit. The 3-D structures of a number of NHases have been determined. The α subunit consists of a long extended N-terminal "arm", containing two α-helices, and a C-terminal domain with an unusual four-layered structure (α-β-β-α). The β subunit consists of a long N-terminal loop that wraps around the α subunit; a helical domain that packs with N-terminal domain of the α subunit; and a C-terminal domain consisting of a β-roll and one short helix.
Enzymatic mechanism
The metal centre is located in the central cavity at the interface between two subunits. All protein ligands to the metal atom are provided by the α subunit. The protein ligands to the iron are the sidechains of the three cysteine (Cys) residues and two mainchain amide nitrogens. The metal ion is octahedrally coordinated, with the protein ligands at the five vertices of an octahedron. The sixth position, accessible to the active site cleft, is occupied either by NO or by a solvent-exchangeable ligand (hydroxide or water). The two Cys residues coordinated to the metal are post-translationally modified to Cys-sulfinic (Cys-SO2H) and -sulfenic (Cys-SOH) acids.
References
- ^ Foerstner KU, Doerks T, Muller J, Raes J, Bork P (2008). "A nitrile hydratase in the eukaryote Monosiga brevicollis". PLoS ONE. 3 (12): e3976. doi:10.1371/journal.pone.0003976. PMC 2603476. PMID 19096720.
{{cite journal}}: CS1 maint: multiple names: authors list (link) CS1 maint: unflagged free DOI (link)
Further reading
- Rzeznicka, K; Schätzle, S; Böttcher, D; Klein, J; Bornscheuer, UT (2009). "Cloning and functional expression of a nitrile hydratase (NHase) from Rhodococcus equi TG328-2 in Escherichia coli, its purification and biochemical characterisation". Appl Microbiol Biotechnol. doi:10.1007/s00253-009-2153-y. PMID 19662400.
{{cite journal}}: Unknown parameter|month=ignored (help) - Song, L; Wang, M; Yang, X; Qian, S (2007). "Purification and characterization of the enantioselective nitrile hydratase from Rhodococcus sp. AJ270". Biotechnol J. 2 (6): 717–24. doi:10.1002/biot.200600215. PMID 17330219.
{{cite journal}}: Unknown parameter|month=ignored (help) - Miyanaga, A; Fushinobu, S; Ito, K; Shoun, H; Wakagi, T (2004). "Mutational and structural analysis of cobalt-containing nitrile hydratase on substrate and metal binding". Eur J Biochem. 271 (2): 429–38. PMID 14717710.
{{cite journal}}: Unknown parameter|month=ignored (help) - Hann, EC; Eisenberg, A; Fager, SK; Perkins, NE; Gallagher, FG; Cooper, SM; Gavagan, JE; Stieglitz, B; Hennessey, SM; DiCosimo, R (1999). "5-Cyanovaleramide production using immobilized Pseudomonas chlororaphis B23". Bioorg Med Chem. 7 (10): 2239–45. PMID 10579532.
{{cite journal}}: Unknown parameter|month=ignored (help)