A biosynthetic pathway for (E)-methyl cinnamate formation in the ectomycorrhizal fungus Tricholoma matsutake

Abstract A biosynthetic pathway for ( E )-methyl cinnamate formation was evaluated in Tricholoma matsutake by tracer experiments using 13 C- and 2 H-labeled precursors. One hundred percent selective 13 C incorporation was observed when l -[1,2,3,4,5,6,7,8,9- 13 C 9 , 15 N]phenylalanine was converted to ( E )-[1,2,3,4,5,6,7,8,9- 13 C 9 ]cinnamate and ( E )-[1,2,3,4,5,6,7,8,9- 13 C 9 ]methyl cinnamate. Similarly, 100% selective 13 C incorporation was observed when ( E )-[1,2,3,4,5,6,7,8,9- 13 C 9 ]cinnamate was converted to ( E )-[1,2,3,4,5,6,7,8,9- 13 C 9 ]methyl cinnamate. In contrast, the 2 H incorporation selectivities were 82.1% and 81.4% when l -[2,3,4,5,6,7,7,8- 2 H 8 ]phenylalanine was converted to ( E )-[2,3,4,5,6,7,8- 2 H 7 ]cinnamate and ( E )-[2,3,4,5,6,7,8- 2 H 7 ]methyl cinnamate, respectively. Thus, T. matsutake synthesizes ( E )-methyl cinnamate from l -phenylalanine via ( E )-cinnamate. ( E )-cinnamate was likely formed through two pathways: one was major and the other was a minor.