title: Chlorophylls of the c family: absolute configuration and inhibition of NADPH:protochlorophyllide oxidoreductase.
abstract: Using circular dichroism (CD) spectroscopy, the stereochemistry at C-13(2) of members of the chlorophyll (Chl) c family, namely Chls c(1), c(2), c(3) and [8-vinyl]-protochlorophyllide a (Pchlide a) was determined. By comparison with spectra of known enantiomers, all Chl c members turned out to have the (R) configuration, which is in agreement with considerations drawn from chlorophyll biosynthesis. Except for a double bond in the side chain at C-17, the chemical structure of Chl c(1) is identical with Pchlide a, the natural substrate of the light-dependent NADPH:protochlorophyllide oxidoreductase (POR). Thus, lack of binding to the active site due to the wrong configuration at C-13(2), which had been proposed previously, cannot be an explanation for inactivity of Chl c in this enzymic reaction. Our results show rather that Chl c(1) is a competitive inhibitor for this enzyme, tested with Pchlide a and Zn-protopheophorbide a (Zn-Ppheide a) as substrates.
authors.affiliation: Botanisches Institut der Universität München, Menzinger Str. 67, D-80638, Munich, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Helfrich
authors.forename: Birgit
authors.initials: B
authors.lastname: Bommer
authors.forename: Ulrike
authors.initials: U
authors.lastname: Oster
authors.forename: Harald
authors.initials: H
authors.lastname: Klement
authors.forename: Karl
authors.initials: K
authors.lastname: Mayer
authors.forename: Antony W D
authors.initials: AW
authors.lastname: Larkum
authors.forename: Wolfhart
authors.initials: W
authors.lastname: Rüdiger
mesh_terms: D002734:Chlorophyll / Q000378:metabolism*; D000077194:Chlorophyll A; D002942:Circular Dichroism; D010088:Oxidoreductases / Q000737:chemistry* / Q000378:metabolism; D044925:Oxidoreductases Acting on CH-CH Group Donors; D000459:Phaeophyceae / Q000737:chemistry / Q000378:metabolism; D011487:Protein Conformation; D011521:Protochlorophyllide / Q000378:metabolism
chemical_list: D002734:Chlorophyll; C064041:chlorophyll c; D011521:Protochlorophyllide; D010088:Oxidoreductases; D044925:Oxidoreductases Acting on CH-CH Group Donors; C023886:protochlorophyllide reductase; D000077194:Chlorophyll A