Molecular aspects of β-ketoacyl synthase (KAS) catalysis

Abstract

Crystal structure data for Escherichia coli β-ketoacyl synthase (KAS) I with C10 and C12 fatty acid substrates bound in conjunction with results from mutagenizing residues in the active site leads to a model for catalysis. Differences from and similarities to the other Claisen enzymes carrying out decarboxylations reveal two catalytic mechanisms, one for KAS I and KAS II, the other for KAS III and chalcone synthase. A comparison of the structures of KAS I and KAS II does not reveal the basis of chain-length specificity. The structures of the Arabidopsis thaliana KAS family are compared.