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| {{STRUCTURE_1eb9| PDB=1eb9 | SCENE= }} | | {{STRUCTURE_1eb9| PDB=1eb9 | SCENE= }} |
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| '''STRUCTURE DETERMINANTS OF SUBSTRATE SPECIFICITY OF HYDROXYNITRILE LYASE FROM MANIHOT ESCULENTA'''
| | ===STRUCTURE DETERMINANTS OF SUBSTRATE SPECIFICITY OF HYDROXYNITRILE LYASE FROM MANIHOT ESCULENTA=== |
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| ==Overview==
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| Tryptophan 128 of hydroxynitrile lyase of Manihot esculenta (MeHNL) covers a significant part of a hydrophobic channel that gives access to the active site of the enzyme. This residue was therefore substituted in the mutant MeHNL-W128A by alanine to study its importance for the substrate specificity of the enzyme. Wild-type MeHNL and MeHNL-W128A showed comparable activity on the natural substrate acetone cyanohydrin (53 and 40 U/mg, respectively). However, the specific activities of MeHNL-W128A for the unnatural substrates mandelonitrile and 4-hydroxymandelonitrile are increased 9-fold and approximately 450-fold, respectively, compared with the wild-type MeHNL. The crystal structure of the MeHNL-W128A substrate-free form at 2.1 A resolution indicates that the W128A substitution has significantly enlarged the active-site channel entrance, and thereby explains the observed changes in substrate specificity for bulky substrates. Surprisingly, the MeHNL-W128A--4-hydroxybenzaldehyde complex structure at 2.1 A resolution shows the presence of two hydroxybenzaldehyde molecules in a sandwich type arrangement in the active site with an additional hydrogen bridge to the reacting center.
| | The line below this paragraph, {{ABSTRACT_PUBMED_11742123}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 11742123 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_11742123}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Hydroxynitrile lyase]] | | [[Category: Hydroxynitrile lyase]] |
| [[Category: Substrate specificity]] | | [[Category: Substrate specificity]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 14:53:47 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 00:26:37 2008'' |
