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Origin of the p K a shift of the catalytic lysine in acetoacetate decarboxylase
Author(s) -
Ishikita Hiroshi
Publication year - 2010
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.2010.07.003
Subject(s) - protonation , chemistry , solvation , catalysis , aqueous solution , residue (chemistry) , lysine , active site , crystal structure , stereochemistry , crystallography , solvent , organic chemistry , biochemistry , amino acid , ion
The p K a value of Lys115, the catalytic residue in acetoacetate decarboxylate, was calculated using atomic coordinates of the X‐ray crystal structure with consideration of the protonation states of all titratable sites in the protein. The calculated p K a value of Lys115 (p K a (Lys115)) was unusually low (≈6) in agreement with the experimentally measured value. Although charged residues impact p K a (Lys115) considerably in the native protein, the significant p K a (Lys115) downshift in the protein with respect to aqueous solution was mainly due to loss of the solvation energy in the catalytic active site relative to bulk water.