PHYSIOLOGY AND METABOLISM-YfcX Enables Medium-Chain-Length Poly (3-Hydroxyalkanoate) Formation from Fatty Acids in Recombinant Escherichia coli fadB Strains

摘要: Expression of Escherichia coli open reading frame yfcX is shown to be required for medium-chain-length polyhydroxyalkanoate (PHAMCL) formation from fatty acids in an E. coli fadB mutant. The open reading frame encodes a protein, YfcX, with significant similarity to the large subunit of multifunctional beta-oxidation enzymes. E. coli fadB strains modified to contain an inactivated copy of yfcX and to express a medium-chain-length synthase are unable to form PHAMCLs when grown in the presence of fatty acids. Plasmid-based expression of yfcX in the FadB- YfcX- PhaC+ strain restores polymer formation. YfcX is shown to be a multifunctional enzyme that minimally encodes hydratase and dehydrogenase activities. The gene encoding YfcX is located downstream from yfcY, a gene encoding thiolase activity. Results of insertional inactivation studies and enzyme activity analyses suggest a role for yfcX in PHA …