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Conversion of GA5 to GA6 and GA3 in Cell-free Systems from Phaseolus vulgaris and Oryza sativa a



Masatomo Kobayashi , Sang-Soo Kwak , Yuji Kamiya , Hisakazu b



Yamane , Nobutaka Takahashi & Akira Sakurai a

The Institute of Physical and Chemical Research, Wako-shi, Saitama 351–01, Japan b

Department of Agricultural Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo 113, Japan Published online: 08 Sep 2014.

To cite this article: Masatomo Kobayashi, Sang-Soo Kwak, Yuji Kamiya, Hisakazu Yamane, Nobutaka Takahashi & Akira Sakurai (1991) Conversion of GA5 to GA6 and GA3 in Cell-free Systems from Phaseolus vulgaris and Oryza sativa, Agricultural and Biological Chemistry, 55:1, 249-251 To link to this article:

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Agric. BioI. Chem., 55 (1), 249-251, 1991


,Conversion of GAs to ·GA 6 and GA3 in Cell-free S'ys~e,ms from Phaseolus vulgaris ,andOryza sativa'

Downloaded by [RIKEN] at 21:59 19 February 2015

Masatomo KOBAYASHI, Sang-Soo KWAK,t Yuji KAMIYA, . Hisakazu .YAMANE,* Nobutaka TAKAHASHI* and Akira SAKURAI The: Institute of Physical andChemicalResearch, Wako-:-shi, Saitama 351-01, Japan * Department of Agricultural Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo 113, Japan

Received May 28, 1990

Gibberellin As has. been identified in several plants, 1) and it shows activities, on variousbioassays. 2) In these bioassays, GAs promotes the shoot elongation of normal rice, cultivar Nih()nbare, at the same level as GAl. Howev~r, it does not promote shoot elongation of dwarf rice, cultivarWaito-C" which is. a deficieI,lt l,1lutant of 3f)-hydroxylation oCgibberellins. 3 ) This suggests that GAs is not per se ~ctive,in rice, but that it becomes active by conversion to an active gibberellin in rice. The conversion of GAs tOGA 3 in intact shoots of Zea rrzays4) and in cell-free extracts of Marah macroc~rpusS)has been shown. However, the metaboli~m oLGA s in cell-free extracts from Phaseolus vulgaris (Leguminosae) apd Oryza. sativa (Gramineae) has not been confirmed. We report here the conversion of GAsto GA 6 oLGA3 by' cell·Jree extracts fro;m these plants. In cell-free extracts ofP. vulgaris, ,GA 20 has. been converted to GAl' GAs and GA 6,.6) The detection of GAs :~nd GA 6 in. the metabolites suggests thCl;t the ~xtract converted GAs to GA 6, since GA 6 could be derived from GAs by anepoxidation of its doubleb()nd,atC-2. Contrary to the expectation, GAs was not converted to GA 6 by crude enzyme extracts,probably due to the low activity of the enzyme and/or the presence'of an inhiQitoLIn the course of a study ,on the.substrate specificity of partially, purified 3f)-hydroxylase from P. vulgaris, we found that the addition of. cold .GA s . into the incubation ,mixture, inhibited the conversion of [3HJGA 20 to [3HJGA 1.7) This inhibitory a«.tivity·of GAs implie,s that GAs could be a sub~trate for 3f)-hydro~ylase as well as GA 20 , and be epoxidized to GA 6. Partially purifi:d gibberellin 3f)-hydroxylase from immature seeds of P. 'vulgaris was prepared by methanol t

249 precipitation, hydrophobic .,interaction chromatography and ion exchange chromatography. 8) When [17- 13 C, 3H 2JGA s '(2500 Bq) was incubat~d with a mixture of the enzyme preparation, 2-oxoglutarate, potassium ascorbate and Fe 2 +, a product (486 Bq) was detected at the same retention time as authentic GA 6 by HPLC.This compound was identified as [17- 13 CJGA 6 by full-scan gaschromatography-mass spectrometry (q-C/MS). This result confirmed that the partially purified 3p-hydroxylase catalyzed the epoxidatlon orGAs toGA. 6. The cofactor requirement for the epoxidation of GAs was then studied (Table I). The amount of GA 6 produced without adding Fe 2 + was about one third of the amount when all the other cofactors were present. The' reason, for the reduced a