Abstract
Rosmarinic acid (RA) and its derivants are medicinal compounds that comprise the active components of several therapeutics. We isolated and characterised a tyrosine aminotransferase of Prunella vulgaris (PvTAT). Deduced PvTAT was markedly homologous to other known/putative plant TATs. Cytoplasmic localisation of PvTAT was observed in tobacco protoplasts. Recombinantly expressed and purified PvTAT had substrates preference for L-tyrosine and phenylpyruvate, with apparent Km of 0.40 and 0.48 mM, and favoured the conversion of tyrosine to 4-hydroxyphenylpyruvate. In vivo activity was confirmed by functional restoration of the Escherichia coli tyrosine auxotrophic mutant DL39. Agrobacterium rhizogenes-mediated antisense/sense expression of PvTAT in hairy roots was used to evaluate the contribution of PvTAT to RA synthesis. PvTAT were reduced by 46–95% and RA were decreased by 36–91% with low catalytic activity in antisense transgenic hairy root lines; furthermore, PvTAT were increased 0.77–2.6-fold with increased 1.3–1.8-fold RA and strong catalytic activity in sense transgenic hairy root lines compared with wild-type counterparts. The comprehensive physiological and catalytic evidence fills in the gap in RA-producing plants which didn’t provide evidence for TAT expression and catalytic activities in vitro and in vivo. That also highlights RA biosynthesis pathway in P. vulgaris and provides useful information to engineer natural products.
Highlights
The popular medicinal plant, Prunella vulgaris, known as ‘heal-all’ or ‘self-heal’, has therapeutical applications in alleviating sore throats, reducing fever, and accelerating wound healing[1]
Tyrosine aminotransferase (TAT) reversibly catalyses Tyr to 4-hydroxyphenylpyruvate (4-HPP), which is the substrate for pathways producing plastoquinone[31, 32], tocopherols[33], phenolic acid[14, 28], and benzylisoquinoline alkaloid (BIA)[34] in plants, tyrosine is synthesised from 4-HPP by TAT in bacteria
Many substances are derived from tyrosine, such as Rosmarinic acid (RA), homogentisate, tocopherol, and BIA, which contribute to human health
Summary
The popular medicinal plant, Prunella vulgaris, known as ‘heal-all’ or ‘self-heal’, has therapeutical applications in alleviating sore throats, reducing fever, and accelerating wound healing[1]. TAT reversibly catalyses Tyr to 4-hydroxyphenylpyruvate (4-HPP), which is the substrate for pathways producing plastoquinone[31, 32], tocopherols[33], phenolic acid[14, 28], and benzylisoquinoline alkaloid (BIA)[34] in plants, tyrosine is synthesised from 4-HPP by TAT in bacteria. These natural products increase plant fitness and are linked to potential benefits for human health
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