(3Z)- and (3E)-phytochromobilin are intermediates in the biosynthesis of the phytochrome chromophore
Terry, M.J.., McDowell, M.T. and Lagarias, J.C. (1995) (3Z)- and (3E)-phytochromobilin are intermediates in the biosynthesis of the phytochrome chromophore. Journal of Biological Chemistry, 270, (19), 11111-11118. (PMID:7744741).
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Using a high performance liquid chromatography (HPLC)-based assay, we have demonstrated that isolated oat etioplasts convert the linear tetrapyrrole biliverdin IX alpha to (3E)-phytochromobilin, the proposed precursor of the chromophore of the plant photoreceptor phytochrome. In addition to (3E)-phytochromobilin, the synthesis of a second phytochromobilin was detected by its ability to functionally assemble with recombinant oat apophytochrome A. The structure of this new pigment has been determined to be the 3Z isomer of phytochromobilin by absorption and 1H NMR spectroscopy. Like (3E)-phytochromobilin, assembly of HPLC-purified (3Z)-phytochromobilin with apophytochrome yielded a holoprotein that is spectrally indistinguishable from native oat phytochrome A. However, the postchromatographic conversion of (3Z)- to (3E)-phytochromobilin appears to be responsible for this result. Kinetic HPLC analyses have demonstrated that (3Z)-phytochromobilin is synthesized prior to the 3E isomer by oat etioplasts. We therefore propose that (3Z)-phytochromobilin is the immediate product of biliverdin IX alpha reduction by the enzyme phytochromobilin synthase. This implicates the presence of an isomerase that catalyzes the conversion of (3Z)- to (3E)-phytochromobilin, the immediate precursor of the phytochrome A chromophore.
|Subjects:||Q Science > QH Natural history > QH301 Biology
R Medicine > R Medicine (General)
|Divisions:||University Structure - Pre August 2011 > School of Biological Sciences
|Date Deposited:||12 May 2011 10:55|
|Last Modified:||01 Jun 2011 01:20|
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