Conversion of gibberellin A20 to gibberellins A1 and A5 in a cell-free system from Phaseolus vulgaris

The soluble fraction of a cell-free system from immature seeds of Phaseolus vulgaris L. converts gibberellin A₂₀ (GA₂₀) to GA₁ and GA₅. It does however not metabolize GA₁ and GA₂₉ to GA₅, showing that in this system GA₂₀ is converted directly to GA₅. The steps from GA₂₀ to GA₁ (3-hydroxylation) and from GA₂₀ to GA₅ (² double-bond formation) require oxygen, Fe²⁺ and -ketoglutarate, and are stimulated by ascorbate. The enzymes catalyzing these conversions bate. The enzymes catalyzing these conversions have properties similar to those of GA oxidases found in Cucurbita maxima and Pisum sativum.Abbreviations GA_n gibberellin A_n - HPLC high-performance liquid chromatography - GC-MS combined gas chromatography-mass spectrometry - TLC thin-layer chromatography - TMSi/TMSi trimethylsilyl ether/trimethylsilyl ester Graduate student, University of Tokyo