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Role of zinc ion for catalytic activity in d ‐serine dehydratase from Saccharomyces cerevisiae
Author(s) -
Ito Tomokazu,
Koga Kazushi,
Hemmi Hisashi,
Yoshimura Tohru
Publication year - 2012
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2011.08451.x
Subject(s) - saccharomyces cerevisiae , dehydratase , chemistry , biochemistry , serine , zinc , yeast , enzyme , organic chemistry
d ‐Serine dehydratase from Saccharomyces cerevisiae (DsdSC) is a fold‐type III pyridoxal 5′‐phosphate‐dependent enzyme catalyzing d ‐serine dehydration. The enzyme contains 1 mol Zn 2+ in its active site and shows a unique zinc dependence. The Zn 2+ is essential for the d ‐serine dehydration, but not for the α,β‐elimination of β‐Cl‐ d ‐alanine catalyzed as a side‐reaction. The fact that dehydration of d ‐threonine and d ‐ allo ‐threonine, also catalyzed by DsdSC, is likewise Zn 2+ dependent indicates that Zn 2+ is indispensable for the elimination of hydroxyl group, regardless of the stereochemistry of C β . Removal of Zn 2+ results in a less polar active site without changing the gross conformation of DsdSC. 1 H NMR determined the rates of α‐hydrogen abstraction and hydroxyl group elimination of d ‐serine in 2 H 2 O to be 9.7 and 8.5 s −1 , respectively, while the removal of Zn 2+ abolished both reactions. Mutation of Cys400 or His398 within the Zn 2+ binding sites to Ala endowed DsdSC with similar properties to those of the Zn 2+ ‐depleted wild‐type enzyme: the mutants lost the reactivity toward d ‐serine and d ‐threonine but retained that toward β‐Cl‐ d ‐alanine. 1 H NMR analysis also revealed that both α‐hydrogen abstraction and hydroxyl group elimination from d ‐serine were severely hampered in the C400A mutant. Our data suggest that DsdSC catalyzes the α‐hydrogen abstraction and hydroxyl group elimination in a concerted fashion.