Download MendeleyA single amino acid mutation alters substrate specificity towards l-glucose in a bacterial l-galactose dehydrogenase.
Obara, N., Ito, C., Kawashita, K., Takenoya, M., Kim, M., Ito, S., Sasaki, Y., Nakamura, A., Yajima, S.(2026) Biochem Biophys Rep 48: 102819-102819
- PubMed: 42876446 Search on PubMedSearch on PubMed Central
- DOI: https://doi.org/10.1016/j.bbrep.2026.102819
- Primary Citation Related Structures:
26WE - PubMed Abstract:
Structure-based mutagenesis was performed to modify the substrate specificity of bacterial l-galactose dehydrogenase from Luteolibacter sp. strain LG18, which also exhibits intrinsic l-glucose dehydrogenase activity. Based on previously reported crystal structures of the enzyme in ternary complex with l-galactose or l-glucose and NADP + , an M212Q mutant was generated and found to exhibit a pronounced preference for l-glucose. Kinetic analysis showed that the M212Q mutant displayed an approximately 20-fold higher k cat / K M value for l-glucose than for l-galactose. To elucidate the structural basis of this altered specificity, the X-ray crystal structure of the M212Q mutant complexed with l-glucose and NADP + was determined. Substitution of Met212 with Gln is assumed to disrupt the hydrophobic environment between the residue and the substrates, which may prevent proper binding of l-galactose and resulting in an approximately 350-fold increase in K M compared with the wild type. In contrast, in the l-glucose-bound M212Q structure, a compensatory hydrogen bond is formed between the equatorial 4-OH group of l-glucose and Gln212, stabilizing substrate binding and reducing the K M value to approximately one-quarter of that of the wild type. Furthermore, a BLAST search with Lu-LGDH as a query resulted that homologs containing the glutamine residue at the corresponding position as well as other conserved catalytic and substrate-binding residues were found. With emerging studies on l-glucose biology, these results may contribute to enzymatic approaches for detecting the enzymes acting toward l-glucose, which is generally considered absent in nature.
- Department of Bioscience, Tokyo University of Agriculture, Setagaya-ku, Tokyo, 156-8502, Japan.
Organizational Affiliation:
