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Human glucose‐6‐phosphate dehydrogenase Lysine 205 is dispensable for substrate binding but essential for catalysis
Author(s) -
Bautista JoséM.,
Mason Philip J.,
Luzzatto Lucio
Publication year - 1995
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(95)00474-n
Subject(s) - lysine , biochemistry , threonine , chemistry , enzyme , amino acid , dehydrogenase , arginine , active site , site directed mutagenesis , glucose 6 phosphate dehydrogenase , stereochemistry , mutant , serine , gene
By site‐directed mutagenesis of the cloned human glucose‐6‐phosphate dehydrogenase cDNA, lysine 205 (the residue that after reacting with pyridoxal‐5′‐phosphate renders inactive enzyme) was mutated to threonine (K205T) to remove the amino group, or to arginine (K205R) to displace the position of the amino group, in order to analyze the role of its nucleophilic group in position ϵ. Compared to the wild‐type enzyme, the K205T and K205R mutants retain a specific activity of 2.6 and 11.4%, respectively; their catalytic specificity ( K cat / K m ) is drastically decreased, whereas the K m values for both substrates are only slightly increased. These findings in the light of the 3D structure of G6PD suggest that the ϵ‐amino group of lysine 205 can favour a hydrogen bond within the active pocket essential for catalysis.