Gibberellin Metabolism in Cell-Free Preparations from Phaseolus coccineus

Many studies on the metabolism of gibberellins (GAs) have been made with cell-free preparations following the elucidation of in vitro GA-biosynthesis pathways in preparations derived from the liquid endosperm of immature Cucurbita maxima seed1–3 and cotyledons of developing pea seed.4 The endogenous GAs in the seeds of several species of the Leguminosae are well characterized,5 and the corresponding metabolic pathways fall into distinct categories. Non-and 13-hydroxylated routes leading to the C19 GAs are features of Pisum sativum 4 whereas in Phaseolus vulgaris 3β-and 13-hydroxylations occur.6 There is information on the properties of the enzymes in P. vulgaris seed responsible for 3β-hydroxylation of GA20 to GA1 as well as 2,3-desaturation of GA20 to GA5 and 2β-hydroxylation of GA20 to GA29 and GA1 to GA8.7 There are also reports on the partial purification and characterization of GA 2β-hydroxylases from P. vulgaris and Pisum sativum seed8,9 and a 3β-hydroxylase catalyzing the conversion of GA20 to GA1 from immature seed of P. vulgaris.10