Metabolic engineering of Escherichia coli for optimized biosynthesis of nicotinamide mononucleotide a noncanonical redox cofactor

摘要

Establishing NMN+ Biosynthetic Routes in Escherichia coli. NMN+ is produced in a small amount through the DNA ligase reaction in the E. coli cell. Heterologous enzymes, shown in green, can introduce new routes to generate NMN+. E. coli endogenous genes and transport processes are shown in blue. Pathway 1 introduces an NMN+ synthase from Francisella tularensis to produce NMN+ from NaMN+. Pathway 2, NR salvage, produces NAD+ from NR. Pathway 3, NA salvage, produces NMN+ from NA. The NMN+ transporter PnuC* from Salmonella enterica, shown in orange, enabled transport of NMN+ into the cell. The endogenous pncC, was targeted for gene disruption to prevent NMN+ degradation. In the presence of NAD+, NadR inhibits transcription of the genes involved in de novo NAD+ biosynthesis, nicotinate salvage, and E. coli pnuC. NaMN+, nicotinic acid mononucleotide; NaAD+, nicotinic adenine dinucleotide; NAD+, nicotinamide adenine dinucleotide; NMN+, nicotinamide mononucleotide; NR, nicotinamide riboside; NadD, NaMN adenylyltransferase; NadR, NMN adenylyltransferase; NadE, NAD synthase; Ft NadE*, NMN synthase from Francisella tularensis; PncC, NMN amidohydrolase; NadV, nicotinamide phosphoribosyltransferase; Pnuc, nicotinamide riboside transporter; Pnuc*, a mutant PnuC enabling direct transport of NMN+ across the cell membrane