Die Plant Science Student Conference (PSSC) wird seit 20 Jahren im jährlichen Wechsel von Studierenden der beiden Leibniz-Institute IPK und IPB organisiert. Im Interview erläutern Christina Wäsch (IPK) und Carolin Apel (IPB),…
Über 600 Gäste kamen am 4. Juli ans IPB zur Langen Nacht, die Wissen schafft, um bei unserem Wissenschafts-Quiz-Parcours viel Neues zu erfahren und ihre Kenntnisse unter Beweis zu stellen. Unser Programm in diesem Jahr…
Zakharova, S.; Fulhorst, M.; Luczak, L.; Wessjohann, L.;Synthesis, inhibitory and activation properties of prenyldiphosphate mimics for aromatic prenylations with ubiA-prenyl transferaseARKIVOC200479(2004)DOI: 10.3998/ark.5550190.0005.d10
4-Hydroxybenzoate oligoprenyl transferase from E. coli (ubiA-prenyl transferase) is a crucial enzyme for ubiquinone biosynthesis. It catalyzes the formation of 3-oligoprenyl-4-hydroxybenzoates like geranyl hydroxybenzoate (GHB, 23) from geranyl pyrophosphate (GPP, 22). Several analogues and mimics of geranyl pyrophosphate have been prepared for an examination of their ability to inhibit the enzyme. 7,11-Dimethyl-3-oxododeca-6,10-dienoic acid (2), 3-hydroxy7,11- dimethyldodeca-6,10-dienoic acid (3), 2-hydroxy-4,8-dimethyl-3,7-nonadienylphosphonic acid (4), and tripotassium [[(4E)-5,9-dimethyldeca-4,8-dienyl]phosphinato](difluoro)methylphosphonate (5) were synthesized from geraniol. .-2,.-1-Dihydroxylated farnesyl diphosphate 6 was prepared from trans,trans-farnesol. All compounds were tested for enzyme inhibition in a competitive assay with natural substrate. The effect of these compounds on ubiA-prenyltransferase activity varied substantially, ranging from almost full inhibition to, surprisingly, enhanced enzymatic activity at low concentrations by some compounds. A special, EDTAmodifyable magnesium effect is discussed as potential reason.
Publikation
Brandt, W.; Dessoy, M. A.; Fulhorst, M.; Gao, W.; Zenk, M. H.; Wessjohann, L. A.;A Proposed Mechanism for the Reductive Ring Opening of the Cyclodiphosphate MEcPP, a Crucial Transformation in the New DXP/MEP Pathway to Isoprenoids Based on Modeling Studies and Feeding ExperimentsChemBioChem5311-323(2004)DOI: 10.1002/cbic.200300743
Experimental and theoretical investigations concerning the second‐to‐last step of the DXP/MEP pathway in isoprenoid biosynthesis in plants are reported. The proposed intrinsic or late intermediates 4‐oxo‐DMAPP ( 12 ) and 4‐hydroxy‐DMAPP ( 11 ) were synthesized in deuterium‐ or tritium‐labeled form according to new protocols especially adapted to work without protection of the diphosphate moiety. When the labeled compounds MEcPP ( 7 ), 11 , and 12 were applied to chromoplast cultures, aldehyde 12 was not incorporated. This finding is in agreement with a mechanistic and structural model of the responsible enzyme family: a three‐dimensional model of the fragment L271–A375 of the enzyme GcpE of Streptomyces coelicolor including NADPH, the Fe 4 S 4 cluster, and MEcPP ( 7 ) as ligand has been developed based on homology modeling techniques. The model has been accepted by the Protein Data Bank (entry code 1OX2). Supported by this model, semiempirical PM3 calculations were performed to analyze the likely catalysis mechanism of the reductive ring opening of MEcPP ( 7 ), hydroxyl abstraction, and formation of HMBPP ( 8 ). The mechanism is characterized by a proton transfer (presumably from a conserved arginine 286) to the substrate, accompanied by a ring opening without high energy barriers, followed by the transfer of two electrons delivered from the Fe 4 S 4 cluster, and finally proton transfer from a carboxylic acid side chain to the hydroxyl group to be removed from the ligand as water. The proposed mechanism is in agreement with all known experimental findings and the arrangement of the ligand within the enzyme. Thus, a very likely mechanism for the second to last step of the DXP/MEP pathway in isoprenoid biosynthesis in plants is presented. A principally similar mechanism is also expected for the reductive dehydroxylation of HMBPP ( 8 ) to IPP ( 9 ) and DMAPP ( 10 ) in the last step.