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Fine tuning of coenzyme specificity in family 2 aldo‐keto reductases revealed by crystal structures of the Lys‐274 → Arg mutant of Candida tenuis xylose reductase (AKR2B5) bound to NAD + and NADP +
Author(s) -
Leitgeb Stefan,
Petschacher Barbara,
Wilson David K.,
Nidetzky Bernd
Publication year - 2005
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/j.febslet.2004.12.063
Subject(s) - cofactor , nad+ kinase , mutant , aldo keto reductase , reductase , oxidoreductase , stereochemistry , lysine , wild type , biochemistry , biology , enzyme , chemistry , amino acid , gene
Aldo‐keto reductases of family 2 employ single site replacement Lys → Arg to switch their cosubstrate preference from NADPH to NADH. X‐ray crystal structures of Lys‐274 → Arg mutant of Candida tenuis xylose reductase (AKR2B5) bound to NAD + and NADP + were determined at a resolution of 2.4 and 2.3 Å, respectively. Due to steric conflicts in the NADP + ‐bound form, the arginine side chain must rotate away from the position of the original lysine side chain, thereby disrupting a network of direct and water‐mediated interactions between Glu‐227, Lys‐274 and the cofactor 2′‐phosphate and 3′‐hydroxy groups. Because anchoring contacts of its Glu‐227 are lost, the coenzyme‐enfolding loop that becomes ordered upon binding of NAD(P) + in the wild‐type remains partly disordered in the NADP + ‐bound mutant. The results delineate a catalytic reaction profile for the mutant in comparison to wild‐type.