The role of ala198 in the stability and coenzyme specificity of bacterial formate dehydrogenases

• Published in: Actanaturae 2015-01, Vol.7 (1), p.60-69
• Main Authors: Alekseeva, A A, Fedorchuk, V V, Zarubina, S A, Sadykhov, E G, Matorin, A D, Savin, S S, Tishkov, V I
• Format: Article
• Language: English
• ISSN: 2075-8251
• DOI: 10.32607/20758251-2015-7-1-60-69

It has been shown by an X-ray structural analysis that the amino acid residues Ala198, which are located in the coenzyme-binding domain of NAD(+)-dependent formate dehydrogenases (EC 1.2.1.2., FDH) from bacteria Pseudomonas sp.101 and Moraxella sp. C-1 (PseFDH and MorFDH, respectively), have non-optimal values of the angles ψ and φ. These residues were replaced with Gly by site-directed mutagenesis. The mutants PseFDH A198G and MorFDH A198G were expressed in E.coli cells and obtained in active and soluble forms with more than 95% purity. The study of thermal inactivation kinetics showed that the mutation A198G results in a 2.5- fold increase in stability compared to one for the wild-type enzymes. Kinetic experiments indicate that A198G replacement reduces the KM (NAD+) value from 60 to 35 and from 80 to 45 μM for PseFDH and MorFDH, respectively, while the KM (HCOO-) value remains practically unchanged. Amino acid replacement A198G was also added to the mutant PseFDH D221S with the coenzyme specificity changed from NAD(+) to NADP(+). In this case, an increase in thermal stability was also observed, but the influence of the mutation on the kinetic parameters was opposite: KM increased from 190 to 280 μM and from 43 to 89 mM for NADP(+) and formate, respectively. According to the data obtained, inference could be drawn that earlier formate dehydrogenase from bacterium Pseudomonas sp. 101 was specific to NADP(+), but not to NAD(+).