Identification and characterization of BAHD hydroxycinnamoyltransferases in the fern Neoblechnum brasiliense.

Neoblechnum brasiliense, a leptosporangiate fern of the family Blechnaceae, is known to have a rich phenolic metabolism. Rosmarinic acid and blechnic acid B have been detected beside chlorogenic acid. As BAHD acyltransferases often are responsible for the formation of this kind of esters, for example, rosmarinic acid synthases or 4-coumaroyl-CoA:shikimic or quinic acid hydroxycinnamoyltransferases, nine coding sequences for BAHD acyltransferases were amplified from N. brasiliense and heterologously expressed. All enzymes proved to be active with p-coumaroyl-CoA as acyl donor as well as other hydroxycinnamoyl-CoA derivatives. Four enzymes (NbHCT4, 6, 7, 9) accepted various alcohols and amines but only to a very low extent. High catalytic efficiency was observed for NbHCT1 and 2 that preferred shikimic acid as acceptor substrate, while NbHCT3 was most active with quinic acid and is part of a lineage-specific duplication subclade of clade V with sequences of Cyatheales and Polypodiales. Tryptamine amides were formed by NbHCT5. NbHCT8 not only preferred 3-hydroxyanthranilate but also transformed shikimic and quinic acids. NbHCTs 1, 3, and 8 were fully kinetically characterized. In a phylogenetic tree comprising members of all known BAHD clades, NbHCT1, 2, 3, and 8 were grouped into clade V harboring most known shikimate and quinate hydroxycinnamoyltransferases, while NbHCT6 and 7 were in or near clade VI. NbHCT4 was placed in clade IV, NbHCT5 most probably in clade IV and NbHCT9 in clade I. Since no hydroxycinnamoyltransferase forming rosmarinic acid could be identified, further hydroxycinnamoyltransferases must be expected in N. brasiliense.