Stereoselective biosynthesis of chloroarylpropane diols by the basidiomycete Bjerkandera adusta

Previously we have shown that 1-arylpropane-1,2-diols are catabolic products of image-phenylalanine during idiophasic metabolism of B. adusta that are stereoselectively biosynthesized from a C7-unit (ring + benzylic carbon) and a C2-unit as predominantly erythro 1R, 2S enantiomers. In order to probe the mechanism of 1-arylpropane-1,2-diol formation, the products of the incubation of isotopically labelled aromatic aldehydes as substrates with Bjerkandera adusta (DAOM 215869) have been characterized. The aromatic aldehydes were benzaldehyde (ring D5) and 4-methoxy- and 4-hydroxybenzaldehydes (ring 13C6). These aldehydes were all stereoselectively incorporated into the corresponding 1-arylpropane-1,2-diols, including the chloro analogues, as well as into the corresponding α-ketols (phenyl acetyl carbinols (PAC’s) and 2-hydroxy propiophenones (2-HPP’s)) the presumed precursors of the diols. Benzoic acid (ring D5) was likewise incorporated into the diols, chlorodiols and α-ketols. These results lead us to conclude that the aromatic aldehydes benzaldehyde, 4-hydroxybenzaldehyde and 4-methoxybenzaldehyde are likely C7-unit precursors in the carboligation reaction(s) that leads to 1-arylpropane-1,2-diol biosynthesis. The metabolic role of the diols remains to be elucidated but they may be important intermediates in CAM (chlorinated anisyl metabolite) aldehyde–alcohol cycling and also act as substrates for the chlorination/hydroxylation enzymes yet to be identified in white rot fungi.