Incorporation of 1-(14) carbon-isopentenyldiphosphate, geraniol and farnesol into chlorophyll in plastid membrane fractions of Avena sativa L. [oats]
1981
Benz, J. | Ruediger, W. (Muenchen Univ. (Germany, F.R.). Inst. fuer Botanik)
Incorporation of 1-(14)C-isopentenyldiphosphate (IPP) and related diprenyl and triprenyl substrates into chlorophyll of irradiated etioplast membranes of Avena sativa L. was investigated. The etioplast membranes contain the enzyme chlorophyll synthetase which catalyzes the esterification of chlorophyllide with exogenous substrates like geranylgeranyl diphosphate or geranylgeraniol plus adenosine triphosphate. The main product after incubation with IPP, IPP plus geraniol/ATP, IPP plus farnesol/ATP or IPP plus farnesyl diphosphate was ChlGG, followed by Chl(H2)GG, Chl(H4)GG and Chlp. Increased yields of Chlp after incubation with farnesyl diphosphate with or without IPP were due to increased mobilization of endogenous substrates. The specific radioactivities of ChlGG after incubation with IPP plus farnesol, IPP plus geraniol or IPP alone indicated the incorporation of one, two or three mols IPP, respectively, into one mol geranylgeraniol. Specific radioactivities of esterified chlorophyll a plus geranylgeraniol were somewhat, that of Chl(H4)GG and Chlp considerably smaller than that of ChlGG. The results confirmed earlier observations on the following sequential steps for chlorophyll biosynthesis: Chlide versus ChlGG versus ChlH2GG versus ChlH4GG versus Chl-phytol.
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