BIOSYNTHETIC-PATHWAY FOR VERATRYL ALCOHOL IN THE LIGNINOLYTIC FUNGUS PHANEROCHAETE-CHRYSOSPORIUM

Veratryl alcohol (VA) is a secondary metabolite of white-rot fungi that produce the ligninolytic enzyme lignin peroxidase. VA stabilizes lignin peroxidase, promotes the ability of this enzyme to oxidize a variety of physiological substrates, and is accordingly thought to play a significant role in fungal ligninolysis. Pulse-labeling and isotope-trapping experiments have now clarified the pathway for VA biosynthesis in the white-rot basidiomycete Phanerochaete chrysosporium. The pulse-labeling data, obtained with C-14-labeled phenylalanine, cinnamic acid, benzoic acid, and benzaldehyde, showed that radiocarbon labeling followed a reproducible sequence: it peaked first in cinnamate, then in benzoate and benzaldehyde, and finally in VA. Phenylalanine, cinnamate, benzoate, and benzaldehyde were all efficient precursors of VA in vivo. The isotope-trapping experiments sho,ved that exogenous, unlabeled benzoate and benzaldehyde were effective traps of phenylalanine-derived C-14. These results support a pathway in which VA biosynthesis proceeds as follows: phenylalanine --> cinnamate --> benzoate and/or benzaldehyde --> VA.