Reaction participants Show >> << Hide
- Name help_outline 2-hydroxy-2-methylpropanenitrile Identifier CHEBI:15348 (CAS: 75-86-5) help_outline Charge 0 Formula C4H7NO InChIKeyhelp_outline MWFMGBPGAXYFAR-UHFFFAOYSA-N SMILEShelp_outline CC(C)(O)C#N 2D coordinates Mol file for the small molecule Search links Involved in 4 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline acetone Identifier CHEBI:15347 (Beilstein: 635680; CAS: 67-64-1) help_outline Charge 0 Formula C3H6O InChIKeyhelp_outline CSCPPACGZOOCGX-UHFFFAOYSA-N SMILEShelp_outline CC(C)=O 2D coordinates Mol file for the small molecule Search links Involved in 15 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline hydrogen cyanide Identifier CHEBI:18407 (CAS: 74-90-8) help_outline Charge 0 Formula CHN InChIKeyhelp_outline LELOWRISYMNNSU-UHFFFAOYSA-N SMILEShelp_outline C#N 2D coordinates Mol file for the small molecule Search links Involved in 45 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
Cross-references
| RHEA:11932 | RHEA:11933 | RHEA:11934 | RHEA:11935 | |
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| Reaction direction help_outline | undefined | left-to-right | right-to-left | bidirectional |
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Publications
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Reaction mechanism of hydroxynitrile lyases of the alpha/beta-hydrolase superfamily: the three-dimensional structure of the transient enzyme-substrate complex certifies the crucial role of LYS236.
Gruber K., Gartler G., Krammer B., Schwab H., Kratky C.
The hydroxynitrile lyases (HNLs) from Hevea brasiliensis (HbHNL) and from Manihot esculenta (MeHNL) are both members of the alpha/beta-hydrolase superfamily. Mechanistic proposals have been put forward in the past for both enzymes; they differed with respect to the role of the active-site lysine r ... >> More
The hydroxynitrile lyases (HNLs) from Hevea brasiliensis (HbHNL) and from Manihot esculenta (MeHNL) are both members of the alpha/beta-hydrolase superfamily. Mechanistic proposals have been put forward in the past for both enzymes; they differed with respect to the role of the active-site lysine residue for which a catalytic function was claimed for the Hevea enzyme but denied for the Manihot enzyme. We applied a freeze-quench method to prepare crystals of the complex of HbHNL with the biological substrate acetone cyanohydrin and determined its three-dimensional structure. Site-directed mutagenesis was used to prepare the mutant K236L, which is inactive although its three-dimensional structure is similar to the wild-type enzyme. However, the structure of the K236L-acetone cyanohydrin complex shows the substrate in a different orientation from the wild-type complex. Finite difference Poisson-Boltzmann calculations show that in the absence of Lys(236) the catalytic base His(235) would be protonated at neutral pH. All of this suggests that Lys(236) is instrumental for catalysis in several ways, i.e. by correctly positioning the substrate, by stabilizing the negatively charged reaction product CN(-), and by modulating the basicity of the catalytic base. These data complete the elucidation of the reaction mechanism of alpha/beta-hydrolase HNLs, in which the catalytic triad acts as a general base rather than as a nucleophile; proton abstraction from the substrate is performed by the serine, and reprotonation of the product cyanide is performed by the histidine residues. Together with a threonine side chain, the active-site serine and lysine are also involved in substrate binding. << Less