Fungal products. Part XIV. Metabolic pathways from ent-kaurenoic acid to the fungal gibberellins in mutant B1-41a of Gibberella fujikuroi

Abstract

The metabolism of substrates normally produced by wild-type strains of Gibberella fujikuroi has been determined in resuspended cultures of the mutant B1-41a at pH 3·5 and 7·0. The metabolites were identified by g.l.c.–mass spectrometry and g.l.c.–radio-counting. From the results at pH 3·5 the metabolic steps from ent-kaurenoic acid to the fungal gibberellins have been deduced. The oxidation level at which C-20 is lost in the formation of the C₁₉-gibberellins could not be determined. ent-7-Oxokaurenoic acid does not serve as a precursor of gibberellin A₁₂ aldehyde. At pH 7·0 the pathway from gibberellin A₁₂ is diverted completely to 3-deoxygibberellins such as gibberellin A₉.