title: Functional characterization of the first two actinomycete 4-amino-4-deoxychorismate lyase genes.
abstract: In some antibiotic producers, p-aminobenzoic acid (PABA) or its immediate precursor, 4-amino-4-deoxychorismate (ADC), is involved in primary metabolism and antibiotic biosynthesis. In Streptomyces sp. FR-008, a gene pabC-1 putatively encoding a fold-type IV pyridoxal 5'-phosphate (PLP)-dependent enzyme was found within the antibiotic FR-008/candicidin biosynthetic gene cluster, whose inactivation significantly reduced the productivity of antibiotic FR-008 to about 20% of the wild-type level. Its specific role in PABA formation was further demonstrated by the successful complementation of an Escherichia coli pabC mutant. Moreover, a free-standing gene pabC-2, probably encoding another fold-type IV PLP-dependent enzyme, was cloned from the same strain. Inactivation of pabC-2 reduced antibiotic FR-008 yield to about 57% of the wild-type level in the mutant, and the complementation of the E. coli pabC mutant established its involvement in PABA biosynthesis. Furthermore, a pabC-1/pabC-2 double mutant only retained about 4% of the wild-type antibiotic FR-008 productivity, clearly indicating that pabC-2 also contributed to biosynthesis of this antibiotic. Surprisingly, apparently retarded growth of the double mutant was observed on minimal medium, which suggested that both pabC-1 and pabC-2 are involved in PABA biosynthesis for primary metabolism. Finally, both PabC-1 and PabC-2 were shown to be functional ADC lyases by in vitro enzymic lysis with the release of pyruvate. pabC-1 and pabC-2 appear to represent the first two functional ADC lyase genes identified in actinomycetes. The involvement of these two ADC lyase genes in both cell growth and antibiotic FR-008 biosynthesis sets an example for the interplay between primary and secondary metabolisms in bacteria.
authors.affiliation: Laboratory of Microbial Metabolism and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200030, China.
authors.forename: Yirong
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Laboratory of Microbial Metabolism and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200030, China.
authors.forename: Linquan
authors.initials: L
authors.lastname: Bai
authors.affiliation: Laboratory of Microbial Metabolism and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200030, China.
authors.forename: Zixin
authors.initials: Z
authors.lastname: Deng
mesh_terms: D010129:4-Aminobenzoic Acid / Q000378:metabolism; D039903:Actinobacteria / Q000201:enzymology* / Q000235:genetics; D002174:Candicidin / Q000096:biosynthesis; D003001:Cloning, Molecular; D017353:Gene Deletion; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D005810:Multigene Family; D007652:Oxo-Acid-Lyases / Q000235:genetics / Q000378:metabolism; D011732:Pyridoxal Phosphate / Q000378:metabolism
chemical_list: D002174:Candicidin; D011732:Pyridoxal Phosphate; D007652:Oxo-Acid-Lyases; C066600:aminodeoxychorismate lyase; D010129:4-Aminobenzoic Acid