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Both histidine residues of the conserved HHXXXDG motif are essential for wax ester synthase/acyl‐CoA:diacylglycerol acyltransferase catalysis
Author(s) -
Stöveken Tim,
Kalscheuer Rainer,
Steinbüchel Alexander
Publication year - 2009
Publication title -
european journal of lipid science and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.614
H-Index - 94
eISSN - 1438-9312
pISSN - 1438-7697
DOI - 10.1002/ejlt.200800167
Subject(s) - acyltransferases , histidine , biochemistry , diacylglycerol kinase , active site , enzyme , chemistry , acyl coa , residue (chemistry) , stereochemistry , biosynthesis , protein kinase c
Bacterial acyltransferases of the wax ester synthase/diacylglycerol acyltransferase (WS/DGAT) family possess a highly conserved HHXXXDG motif. In this study, we describe the first experimental evidence that this motif is part of the active site of WS/DGAT from the Acinetobacter baylyi strain ADP1 and that it is crucial for enzymatic activity. The second histidine residue of this motif (H 133 ) turned out to be essential for the catalytic activity. In addition, the replacement of the first histidine (His 132 ) also led to explicitly decreased activity. A complete loss of activity was only observed upon substitution of both histidine residues by leucine, revealing that both are necessary for maximal activity. In contrast, the replacement of Asp 137 and Gly 138 against alanine had only little effect on enzyme activity, thus demonstrating that they are not essential for WS/DGAT catalysis although belonging to the highly conserved motif. One peculiarity of WS/DGAT enzymes is their little substrate specificity regarding hydrophobic compounds. In this study, we demonstrated the inability of WS/DGAT to accept polar compounds as substrates.