Non-discriminatory incorporation of L-phenylalanine and L-tyrosine into cinnamoyl part of mulberroside A, a stilbene di-glucoside, in Morus alba cell cultures

摘要

Morus alba callus and cell suspension cultures specifically produce chalcone, 2-arylbenzofuran, and stilbene derivatives, all biosynthetically originated from cinna-moylpolyketide intermediates (Hano et al. 1989, 1994a, 1997). In a feeding experiment with ~(13)C-labeled L-phenylalanine and L-tyrosine, both aromatic amino acids were incorporated intact into cinnamoyl moieties of chalcomoracin (CAL), the Diels-Alder type adduct of chalcone and 2-arylbenzofuran derivatives in the cell cultures (Hano et al. 1994b, c). Furthermore, intact incorporation of ~(13)C-labeled cinnamic acid N-acetyl cys-teamine thioester, an analog of cinnamoyl CoA, into CAL confirmed the pathway leading to p-coumaroyl CoA from L-phenylalanine via cinnamoyl CoA in the M. alba cell cultures (Hano et al. 1999). Direct conversion of L-phenylalanine to L-tyrosine is negligible, because of the absence of the enzyme L-phenylalanine hy-droxylase in higher plants (Weis and Edwards 1980). Hence, the involvement of L-tyrosine in the synthesis of the cinnamoyl moiety of CAL was suggestive of a parallel contribution of the two aromatic amino acids to the formation of the p-coumaroyl parts of CAL.