| Among more than50000secondary metabolites of plants,12000are alkaloids.Caffeine, a typical one, is found in coffee (Coffea arabica), tea (Camellia simensis),cola (Cola nitida). As a special functional substances, caffeine has been widely usedin drugs and foods.Biosynthesis of caffeine occurs mainly in leaves, although it is also observed inother organs. The biosynthetic pathway of caffeine has been intensively studied:methylation of xanthosind, yielding7-methylxanthosine, whose ribose residue isremoved to be7-methylxanthine. The resulting7-methylxanthine is methylated,producing theobromine, which is again methylated to be caffeine.In the present study, the key enzymes involved in the biosynthesis of caffeinehave been cloned from coffee. The genes of N-methyltransferases have been clonedfrom tea leaves. Therefore, the study of enzymes N-methynucleosidase has no report.Consumers concerned about the possible adverse effects of caffeine consumptionwill welcome the caffeine-free drinks. As a nervous stimulant, caffeine still in shortsupply. The large-scale production of transgenic caffeine-deficient Camellia sinensisplants may thus be a more practical proposition, but first some information is neededabout the genes controlling key conversions in the biosynthesis of caffeine, especiallythe N-methynucleosidase.This objective of the research was to screen three suspected N-Methynucleosidase(STx) from leaves of tea in tea genomic libray. The three genes wereintroduced into E.coli cells and induced to expression. The results are following:1. The three N-methy nucleosidase were all introduced into E.coli pGEX-4t-2.They induced to espree the soluble proteins.2. STx can directly catalyze the conversion form XR to X.3.Mix the two enzymes, STx and CaXMT, the content of7-MX is same likeCaXMT only.Because of the absence of the7-MXR, which is the substrate, enzymes activitiesof STx can not be notarized. |
PDF Full Text Request