Changing the reaction specificity of a pyridoxal-5'-phosphate-dependent enzyme.
Graber, R., Kasper, P., Malashkevich, V.N., Sandmeier, E., Berger, P., Gehring, H., Jansonius, J.N., Christen, P.(1995) Eur J Biochem 232: 686-690
- PubMed: 7556224 
- DOI: https://doi.org/10.1111/j.1432-1033.1995.tb20861.x
- Primary Citation of Related Structures:  
1ARG, 1ARH - PubMed Abstract: 
The electron distribution in the coenzyme-substrate adduct of aspartate aminotransferase was changed by replacing active-site Arg386 with alanine and introducing a new arginine residue nearby. [Y225R, R386A]Aspartate aminotransferase decarboxylates L-aspartate to L-alanine (kcat = 0.04 s-1), while its transaminase activity towards dicarboxylic amino acids is decreased by three orders of magnitude (kcat = 0.19 s-1). Molecular-dynamics simulations based on the crystal structure of the mutant enzyme suggest that a new hydrogen bond to the imine N atom of the pyridoxal-5'-phosphate- aspartate adduct and an altered electrostatic potential around its beta-carboxylate group underlie the 650,000-fold increase in the ratio of beta-decarboxylase/transaminase activity.
Organizational Affiliation: 
Biochemisches Institut, Universität Zürich, Switzerland.