Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:4.1.1.32 (phosphoenolpyruvate carboxykinase)
 4,204 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The leafless amphibious sedge Eleocharis vivipara develops culms with C(4) traits and Kranz anatomy under terrestrial conditions, but develops culms with C(3) traits and non-Kranz anatomy under submerged conditions. The culms of the terrestrial form have high C(4) enzyme activities, while those of the submerged form have decreased C(4) enzyme activities. The culms accumulate ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) in the mesophyll cells (MC) and the bundle sheath cells. The Rubisco in the MC may be responsible for the operation of the C(3) pathway in the submerged form. To verify the presence of the C(3) cycle in the MC, we examined the effects of 3,3-dichloro-2-(dihydroxyphosphinoylmethyl) -propenoate (DCDP), an inhibitor of phosphoenolpyruvate carboxylase (PEPC), on photosynthesis in culms of the terrestrial forms of E. vivipara and related amphibious species, E. baldwinii and E. retroflexa ssp. chaetaria. When 1 mM DCDP was fed via the transpiration stream to excised leaves, photosynthesis was inhibited completely in Fimbristylis dichotoma (C(4) control), but by only 20% in potato (C(3) control). In the terrestrial Eleocharis plants, the degree of inhibition of photosynthesis by DCDP was intermediate between those of the C(4) and C(3) plants, at 58-81%. These results suggest that photosynthesis under DCDP treatment in the terrestrial Eleocharis plants is due mainly to fixation of atmospheric CO(2) by Rubisco and probably the C(3) cycle in the MC. These features are reminiscent of those in C(4)-like plants. Differential effects of DCDP on photosynthesis of the 3 Eleocharis species are discussed in relation to differences in the degree of Rubisco accumulation and C(3) activity in the MC.
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PMID:Effects of an inhibitor of phosphoenolpyruvate carboxylase on photosynthesis of the terrestrial forms of amphibious Eleocharis species. 1622 37

The effect of 3,3-dichloro-2-(dihydroxyphosphinoylmethyl)-propenoate (DCDP), an analog of phosphoenolpyruvate (PEP), on PEP carboxylase activity in crude leaf extracts and on photosynthesis of excised leaves was examined. DCDP is an effective inhibitor of PEP carboxylase from Zea mays or Panicum miliaceum; 50% inhibition was obtained at 70 or 350 micromolar, respectively, in the presence of 1 millimolar PEP and 1 millimolar HCO(3) (-). When fed to leaf sections via the transpiration stream, DCDP at 1 millimolar strongly inhibited photosynthesis in C(4) species (79-98% inhibition for a range of seven C(4) species), but only moderately in C(3) species (12-46% for four C(3) species), suggesting different mechanisms of inhibition for each photosynthetic type. The response of P. miliaceum (C(4)) net photosynthesis to intercellular pCO(2) showed that carboxylation efficiency, as well as the CO(2) saturated rate, are lowered in the presence of DCDP and supported the view that carboxylation efficiency in C(4) species is directly related to PEP carboxylase activity. A fivefold increase in intercellular pCO(2) over that occurring in P. miliaceum under normal photosynthesis conditions only increased net photosynthesis rate in the presence of 1 millimolar DCDP from zero to about 5% of the maximal uninhibited rate. Therefore, it seems unlikely that direct fixation of atmospheric CO(2) by the bundle sheath cells makes any significant contribution to photosynthetic CO(2) assimilation in C(4) species. The results support the concept that C(4)-selective herbicides may be developed based on inhibitors of C(4) pathway reactions.
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PMID:Effects of the Phosphoenolpyruvate Carboxylase Inhibitor 3,3-Dichloro-2-(Dihydroxyphosphinoylmethyl)propenoate on Photosynthesis: C(4) Selectivity and Studies on C(4) Photosynthesis. 1666 89

Photosynthesis rates of detached Panicum miliaceum leaves were measured, by either CO(2) assimilation or oxygen evolution, over a wide range of CO(2) concentrations before and after supplying the phosphoenolpyruvate (PEP) carboxylase inhibitor, 3,3-dichloro-2-(dihydroxyphosphinoyl-methyl)-propenoate (DCDP). At a concentration of CO(2) near ambient, net photosynthesis was completely inhibited by DCDP, but could be largely restored by elevating the CO(2) concentration to about 0.8% (v/v) and above. Inhibition of isolated PEP carboxylase by DCDP was not competitive with respect to HCO(3) (-), indicating that the recovery was not due to reversal of enzyme inhibition. The kinetics of (14)C-incorporation from (14)CO(2) into early labeled products indicated that photosynthesis in DCDP-treated P. miliaceum leaves at 1% (v/v) CO(2) occurs predominantly by direct CO(2) fixation by ribulose 1,5-bisphosphate carboxylase. From the photosynthesis rates of DCDP-treated leaves at elevated CO(2) concentrations, permeability coefficients for CO(2) flux into bundle sheath cells were determined for a range of C(4) species. These values (6-21 micromoles per minute per milligram chlorophyll per millimolar, or 0.0016-0.0056 centimeter per second) were found to be about 100-fold lower than published values for mesophyll cells of C(3) plants. These results support the concept that a CO(2) permeability barrier exists to allow the development of high CO(2) concentrations in bundle sheath cells during C(4) photosynthesis.
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PMID:Inorganic Carbon Diffusion between C(4) Mesophyll and Bundle Sheath Cells: Direct Bundle Sheath CO(2) Assimilation in Intact Leaves in the Presence of an Inhibitor of the C(4) Pathway. 1666 86