1yas
From Proteopedia
| Line 1: | Line 1: | ||
[[Image:1yas.jpg|left|200px]] | [[Image:1yas.jpg|left|200px]] | ||
| - | + | <!-- | |
| - | + | The line below this paragraph, containing "STRUCTURE_1yas", creates the "Structure Box" on the page. | |
| - | + | You may change the PDB parameter (which sets the PDB file loaded into the applet) | |
| - | + | or the SCENE parameter (which sets the initial scene displayed when the page is loaded), | |
| - | + | or leave the SCENE parameter empty for the default display. | |
| - | | | + | --> |
| - | | | + | {{STRUCTURE_1yas| PDB=1yas | SCENE= }} |
| - | + | ||
| - | + | ||
| - | }} | + | |
'''HYDROXYNITRILE LYASE COMPLEXED WITH HISTIDINE''' | '''HYDROXYNITRILE LYASE COMPLEXED WITH HISTIDINE''' | ||
| Line 28: | Line 25: | ||
[[Category: Kratky, C.]] | [[Category: Kratky, C.]] | ||
[[Category: Wagner, U G.]] | [[Category: Wagner, U G.]] | ||
| - | [[Category: | + | [[Category: Cyanhydrin formation]] |
| - | + | [[Category: Cyanogenesis]] | |
| - | [[Category: | + | [[Category: Lyase]] |
| - | [[Category: | + | [[Category: Oxynitrilase]] |
| - | [[Category: | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 16:05:24 2008'' |
| - | + | ||
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | |
Revision as of 13:05, 3 May 2008
HYDROXYNITRILE LYASE COMPLEXED WITH HISTIDINE
Overview
BACKGROUND: Over three thousand species of plants, including important food crops such as cassava, use cyanogenesis, the liberation of HCN upon tissue damage, as a defense against predation. Detoxification of cyanogenic food crops requires disruption of the cyanogenic pathway. Hydroxynitrile lyase is one of the key enzymes in cyanogenesis, catalyzing the decomposition of an alpha-cyanohydrin to form HCN plus the corresponding aldehyde or ketone. These enzymes are also of potential utility for industrial syntheses of optically pure chiral cyanohydrins, being used to catalyze the reverse reaction. We set out to gain insight into the catalytic mechanism of this important class of enzymes by determining the three-dimensional structure of hydroxynitrile lyase from the rubber tree, Hevea brasiliensis. RESULTS: The crystal structure of the enzyme has been determined to 1.9 A resolution. It belongs to the alpha/beta hydrolase superfamily, with an active site that is deeply buried within the protein and connected to the outside by a narrow tunnel. The catalytic triad is made up of Ser80, His235 and Asp207. By analogy with known mechanisms of other members of this superfamily, catalysis should involve an oxyanion hole formed by the main chain NH of Cys81 and the side chains of Cys81 and Thr11. Density attributed to a histidine molecule or ion is found in the active site. CONCLUSIONS: By analogy with other alpha/beta hydrolases, the reaction catalyzed by hydroxynitrile lyase involves a tetrahedral hemiketal or hemiacetal intermediate formed by nucleophilic attack of Ser80 on the substrate, stabilized by the oxyanion hole. The SH group of Cys81 is probably involved in proton transfer between the HCN and the hydroxynitrile OH. This mechanism is significantly different from the corresponding uncatalyzed solution reaction.
About this Structure
1YAS is a Single protein structure of sequence from Hevea brasiliensis. Full crystallographic information is available from OCA.
Reference
Mechanism of cyanogenesis: the crystal structure of hydroxynitrile lyase from Hevea brasiliensis., Wagner UG, Hasslacher M, Griengl H, Schwab H, Kratky C, Structure. 1996 Jul 15;4(7):811-22. PMID:8805565 Page seeded by OCA on Sat May 3 16:05:24 2008
