An extraordinary accumulation of (-)-pinoresinol in cell-free extracts of Forsythia intermedia:  evidence for enantiospecific reduction of (+)-pinoresinol.
Stereoselective and enantiospecific transformation mechanisms in lignan biogenesis are only now yielding to scientific inquiry:  it has been shown that soluble cell-free preparations from Forsythia intermedia catalyse the formation of the enantiomerically pure lignan, (-)-secoisolariciresinol, when incubated with coniferyl alcohol in the presence of NAD(P)H and H2O2.  Surprisingly, (-)-pinoresinol also accumulates in this soluble cell-free assay mixture in > 96% enantiomeric excess, even though it is not the naturally occurring antipode present in Forsythia sp.  But these soluble cell-free preparations do not engender stereoselective coupling; instead, racemic pinoresinols are first formed, catalysed by an H2O2-dependent peroxidase reaction.  An enantiospecific NAD(P)H reductase then converts (+)-pinoresinol, and not the (-)-antipode, into (-)-secoisolariciresinol.  Stereoselective synthesis [correction of syntheis] of (+)-pinoresinol from E-coniferyl alcohol is, however, catalysed by an insoluble enzyme preparation in F. suspensa, obtained following removal of readily soluble and ionically bound enzymes; no exogenously supplied cofactors were required other than oxygen, although the reaction was stimulated by NAD-malate addition.  Thus, the overall biochemical pathway to enantiomerically pure (-)-secoisolariciresinol has been delineated.
Katayama
T
T
Institute of Biological Chemistry, Washington State University, Pullman 99164-6340.
Davin
L B
LB
Lewis
N G
NG
D006861:Hydrogen Peroxide / Q000494:pharmacology; D017705:Lignans / Q000096:biosynthesis / Q000378:metabolism*; D009249:NADP / Q000494:pharmacology; D010088:Oxidoreductases / Q000378:metabolism; D010544:Peroxidases / Q000378:metabolism; D010636:Phenols / Q000378:metabolism; D010936:Plant Extracts / Q000737:chemistry / Q000378:metabolism*; D010944:Plants / Q000201:enzymology / Q000378:metabolism*; D013237:Stereoisomerism
D017705:Lignans; D010636:Phenols; D010936:Plant Extracts; D009249:NADP; D006861:Hydrogen Peroxide; C010559:coniferyl alcohol; D010088:Oxidoreductases; D010544:Peroxidases