title: A template search reveals mechanistic similarities and differences in beta-ketoacyl synthases (KAS) and related enzymes.
abstract: A detailed comparison of the active sites in beta-ketoacyl synthases (KAS) and related enzymes has been made. Using three-dimensional templates of the three catalytic residues to scan the protein structural database reveals differences in both the geometry and the catalytic role of equivalent residues in different members of the family. The template based on the catalytic cysteine and two histidines in the KAS I and II is totally specific for this family, with no false hits. However, the role of the histidines in catalysis is different between KAS I/II and thiolase on the one hand and KAS III/chalcone synthase on the other. In contrast, a template comprising only cysteine and one histidine is not specific with many hits including members of the KAS family, metal binding sites, other active sites in nonhomologous proteins, and some "random" nonactive sites.
authors.affiliation: Department of Biochemistry and Molecular Biology, University College London, London, United Kingdom.
authors.forename: Jennifer H
authors.initials: JH
authors.lastname: Dawe
authors.forename: Craig T
authors.initials: CT
authors.lastname: Porter
authors.forename: Janet M
authors.initials: JM
authors.lastname: Thornton
authors.forename: Alethea B
authors.initials: AB
authors.lastname: Tabor
mesh_terms: D015099:3-Oxoacyl-(Acyl-Carrier-Protein) Synthase / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D019295:Computational Biology / Q000379:methods*; D003545:Cysteine / Q000737:chemistry / Q000378:metabolism; D030562:Databases, Protein; D004798:Enzymes / Q000737:chemistry / Q000378:metabolism; D006639:Histidine / Q000737:chemistry / Q000378:metabolism; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism; D008316:Malonyl Coenzyme A / Q000378:metabolism; D015394:Molecular Structure
chemical_list: D004798:Enzymes; D007527:Isoenzymes; D006639:Histidine; D008316:Malonyl Coenzyme A; D015099:3-Oxoacyl-(Acyl-Carrier-Protein) Synthase; D003545:Cysteine