title: Structure function analysis of benzalacetone synthase from Rheum palmatum.
abstract: Benzalacetone synthase (BAS) is a plant-specific chalcone synthase (CHS) superfamily type III polyketide synthase (PKS) that catalyzes a one-step decarboxylative condensation of 4-coumaroyl-CoA with malonyl-CoA. The diketide forming activity of Rheum palmatum BAS is attributed to the characteristic substitution of the conserved active-site Phe215 with Leu (numbering in Medicago sativa CHS). To further understand the structure and function of R. palmatum BAS, four site-directed mutants (C197T, C197G, G256L, and S338V) were newly constructed. All the mutants did not change the product pattern, however, the activity was 2-fold increased in S338V, while reduced to half in G256L mutant. On the other hand, the C197 mutants were functionally almost identical to wild-type BAS, excluding the possibility that the second active-site Cys is involved in the enzyme reaction. Instead, homology modeling suggested a possibility that, unlike the case of CHS, BAS utilizes an alternative pocket to lock the coumaroyl moiety for the diketide formation reaction.
authors: School of Pharmaceutical Sciences, The COE21 Program, University of Shizuoka, 52-1 Yada, Shizuoka 422-8526, Japan.
authors: Tsuyoshi
authors: T
authors: Abe
authors: Hiroyuki
authors: H
authors: Morita
authors: Hisashi
authors: H
authors: Noma
authors: Toshiyuki
authors: T
authors: Kohno
authors: Hiroshi
authors: H
authors: Noguchi
authors: Ikuro
authors: I
authors: Abe
mesh_terms: D000214:Acyl Coenzyme A / Q000737:chemistry; D000217:Acyltransferases / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001665:Binding Sites; D002074:Butanones / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008316:Malonyl Coenzyme A / Q000737:chemistry; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D011487:Protein Conformation; D012250:Rheum / Q000201:enzymology*; D013379:Substrate Specificity
chemical_list: D000214:Acyl Coenzyme A; D002074:Butanones; C058644:4-coumaroyl-coenzyme A; D008316:Malonyl Coenzyme A; C025383:benzylideneacetone; D000217:Acyltransferases; C020141:flavanone synthetase