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Abstract
Flavonoids, such as naringenin, are natural products with high bioactivities and pharmaceutical value, whose titer, however, was limited in microbial biosynthesis. Microbes are enabling platforms to acquire naringenin via introduced artificial pathways. The metabolic pathway derived from L-tyrosine for naringenin biosynthesis requires four enzymes, including tyrosine ammonium lyase (TAL), 4-courmarate:CoA ligase (4CL), chalcone synthesis (CHS), and chalcone isomerase (CHI). Investigating enzyme property, the key elements of the pathway, shows insight for future advances. In this thesis, we systemically characterized KM and kcat of RgTAL, Pc4CL, and MsCHI for the first time with sufficient energy and cofactors supply. Meanwhile, the enzyme performance of PhCHS was evaluated by product conversion rate and identified as a rate-limiting enzyme here, with a 3% naringenin conversion. These results implied directions to pathway engineering. The high-efficiency naringenin microbial factory will boost its potential industrial production, and further make great contributions to human health and nutrition.