Abstract
Lithospermum erythrorhizon produces rosmarinic acid (RA), a well-known hydroxycinnamic acid ester. In RA biosynthetic pathway, condensation of 4-coumaroyl CoA derived from phenylalanine, with 4-hydroxyphenyllactic acid (HPL) derived from tyrosine, results in formation of 4-coumaroyl-4'-hydroxyphenyllactic acid (CHPL) catalyzed by rosmarinic acid synthase (RAS). We attempted to isolate a cDNA of RAS from L. erythrorhizon.
To isolate cDNA, we screened cDNA library using informatics analysis of EST data. Four cDNA isolated were encoding acyltransferases (LeHCT1~4) with typical characteristics of the BAHD superfamily. We prepared the recombinant enzyme to characterize its catalytic function. LeHCT1 displayed the activity of RAS using 4-coumaroyl- and caffeoyl CoA and HPL as substrates. Shikimic acid was not able to serve as acyl acceptors. In L. erythrorhizon cell cultures, RA production is rapidly stimulated by addition methyl jasmonate (MJ), but RA activity is not induced. LeHCT1 mRNA was not induced in accordance with this pattern.
