Enhanced transaminase activity of a bifunctional l-aspartate 4-decarboxylase
Journal
Biochemical and Biophysical Research Communications
Journal Volume
356
Journal Volume
356
Journal Issue
2
Journal Issue
2
Pages
368-373
Start Page
368
End Page
373
ISSN
10902104
Date Issued
2007-05-04
Author(s)
Wang, Nai-Chen
Abstract
L-Aspartate 4-decarboxylase (Asd) catalyzes mainly the beta-decarboxylation of aspartate and also transamination with alpha-keto acids. To investigate residues that are critical in directing the reaction pathway, seven point mutations were designed based on the differences between Asd and amiontransferases in conservative amino acid residues. All mutant Asds were purified and characterized. The F204W mutant enhanced aminotransferase activity, and its ratio to beta-decarboxylase activity was 3.8-fold. Its K(m) values for aspartate and alpha-ketoglutarate were 1.3 and 0.17 mM, respectively, representing a large increase in the binding affinity with substrates. The K347R mutation did not increase transaminase activity. The D360P mutation decreased transaminase activity and was more specific in catalyzing beta-decarboxylation reaction. This is the first study that successfully increased transaminase activity in Asd via site-directed mutagenesis. The modeled protein structure reveals how the residue may involve in reaction specificity, providing insights into comprehending the molecular evolution of this bifunctional enzyme.
Subjects
Aminotransferase
Kinetic study
l-Aspartate 4-decarboxylase
Site-directed mutagenesis
SDGs
Type
journal article