1EB9

Structure Determinants of Substrate Specificity of Hydroxynitrile Lyase from Manihot esculenta

Summary for 1EB9

• Entry DOI: 10.2210/pdb1eb9/pdb
• Related: 1DWO 1DWP 1DWQ 1E89 1E8D 1EB8
• Descriptor: HYDROXYNITRILE LYASE, P-HYDROXYBENZALDEHYDE (3 entities in total)
• Functional Keywords: lyase, hydroxynitrile lyase, substrate specificity, active-site tunnel mutant
• Biological source: MANIHOT ESCULENTA (CASSAVA)
• Total number of polymer chains: 2
• Total formula weight: 59928.64

Authors

Lauble, H.,Miehlich, B.,Foerster, S.,Kobler, C.,Wajant, H.,Effenberger, F. (deposition date: 2001-07-24, release date: 2002-01-01, Last modification date: 2023-12-13)

Primary citation

Lauble, H.,Miehlich, B.,Foerster, S.,Kobler, C.,Wajant, H.,Effenberger, F.
Structure Determinants of Substrate Specificity of Hydroxynitrile Lyase from Manihot Esculenta.
Protein Sci., 11:65-, 2002

PubMed Abstract: 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.

PubMed: 11742123
DOI: 10.1110/PS.PS.33702

Experimental method

X-RAY DIFFRACTION (2.1 Å)