Substrate recognition mechanism of thermophilic dual-substrate enzyme.Ura, H., Nakai, T., Kawaguchi, S.I., Miyahara, I., Hirotsu, K., Kuramitsu, S.
(2001) J Biochem 130: 89-98
- PubMed: 11432784
- DOI: https://doi.org/10.1093/oxfordjournals.jbchem.a002966
- Primary Citation of Related Structures:
1B5O, 1B5P, 1GC3, 1GC4, 1GCK, 5BJ3, 5BJ4
- PubMed Abstract:
Aspartate aminotransferase from an extremely thermophilic bacterium, Thermus thermophilus HB8 (ttAspAT), has been believed to be specific for an acidic substrate. However, stepwise introduction of mutations in the active-site residues finally changed its substrate specificity to that of a dual-substrate enzyme. The final mutant, [S15D, T17V, K109S, S292R] ttAspAT, is active toward both acidic and hydrophobic substrates. During the course of stepwise mutation, the activities toward acidic and hydrophobic substrates changed independently. The introduction of a mobile Arg292* residue into ttAspAT was the key step in the change to a "dual-substrate" enzyme. The substrate recognition mechanism of this thermostable "dual-substrate" enzyme was confirmed by X-ray crystallography. This work together with previous studies on various enzymes suggest that this unique "dual-substrate recognition" mechanism is a feature of not only aminotransferases but also other enzymes.
Department of Biology, Graduate School of Science, Osaka University, Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan.