1eb8: Difference between revisions
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==Overview== | ==Overview== | ||
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 ... | 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. | ||
==About this Structure== | ==About this Structure== | ||
1EB8 is a | 1EB8 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Manihot_esculenta Manihot esculenta] with MPD as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Transferred_entry:_3.3.2.4 Transferred entry: 3.3.2.4], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=4.2.1.37 4.2.1.37] Structure known Active Site: ASA. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1EB8 OCA]. | ||
==Reference== | ==Reference== | ||
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[[Category: substrate specificity]] | [[Category: substrate specificity]] | ||
''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on | ''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Mon Nov 5 13:09:10 2007'' | ||
