title: Cloning and characterization of a type III polyketide synthase from Aspergillus niger.
abstract: Type III polyketide synthases (PKSs) are the condensing enzymes that catalyze the formation of a myriad of aromatic polyketides in plant, bacteria, and fungi. Here we report the cloning and characterization of a putative type III PKS from Aspergillusniger, AnPKS. This enzyme catalyzes the synthesis of alkyl pyrones from C2 to C18 starter CoA thioesters with malonyl-CoA as an extender CoA through decaboxylative condensation and cyclization. It displays broad substrate specificity toward fatty acyl-CoA starters to yield triketide and tetraketide pyrones, with benzoyl-CoA as the most preferred starter. The optimal temperature and pH of AnPKS are 50°C and 8, respectively. Under optimal conditions, the enzyme shows the highest catalytic efficiency (k(cat)/K(m)) of 7.4×10(5)s(-1)M(-1) toward benzoyl-CoA. Homology modeling and site-directed mutagenesis were used to probe the molecular basis of its substrate specificity. This study should open doors for further engineering of AnPKS as a biocatalyst for synthesis of value-added polyketides.
authors: Department of Chemical Engineering, Konkuk University, Seoul 143-701, Republic of Korea.
authors: Jinglin
authors: J
authors: Li
authors: Yunzi
authors: Y
authors: Luo
authors: Jung-Kul
authors: JK
authors: Lee
authors: Huimin
authors: H
authors: Zhao
mesh_terms: D000214:Acyl Coenzyme A / Q000378:metabolism*; D001234:Aspergillus niger / Q000201:enzymology* / Q000235:genetics; D003001:Cloning, Molecular; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D048630:Polyketide Synthases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D011485:Protein Binding; D013379:Substrate Specificity
chemical_list: D000214:Acyl Coenzyme A; C037817:benzoyl-coenzyme A; D048630:Polyketide Synthases