重组粘红酵母酪氨酸解氨酶的酶学特性分析OA

Tyrosine ammonia lyase(TAL)is a key enzyme in the biosynthesis of polyphenol compounds such as flavonoids and lignin.This enzyme catalyzes the deamination of L-tyro-sine to produce p-coumaric acid,which can then be converted by other enzymes to naringe-nin,resveratrol,and other polyphenol compounds with important physiological activities.Currently,it remains unclear how the activity of TAL is affected by the substrate,the prod-uct,and the downstream conversion compounds in the polyphenol biosynthetic pathways.To this end,the widely used TAL from Rhodotorula glutinis(RgTAL)was selected and recom-binantly expressed in Escherichia coli,and the purified enzyme was firstly tested for its opti-mal catalytic condition and kinetic property.Then,various compounds were tested for their impact on enzyme activity and kinetics.The results demonstrate that substrate inhibition ex-ists for RgTAL,with an optimal substrate concentration being 3.2 mmol/L.Caffeic acid does not affect enzyme activity.In comparison,p-coumaric acid competitively inhibits enzyme ac-tivity,whereas naringenin and resveratrol noncompetitively inhibit enzyme activity.The over-all extent of inhibition follows the order of p-coumaric acid＞resveratrol＞naringenin.These findings provide new insights into the regulation mechanism of RtgT A L activity,and lay the foundation for rational design of RgTAL and efficient biosynthesis of p-coumaric acid.