Spinach chloroplasts, inhibition

Bromacil and isocil have been found to be potent and specific inhibitors of photosynthesis at the chloroplast level [361]. The uptake of carbon dioxide is blocked in Chlorella pyrenoidosa and growth inhibition parallels the inhibition of carbon dioxide uptake. In Euglena gracilis and in spinach chloroplasts, the blockage of oxygen production was noted [361]. 

Table II Inhibition of Hill Reaction in Spinach Chloroplasts...

Other orchid metabolites suchs as batatasin 1, inhibited the growth of liverworts, algae and oat coleoptiles. Batatasin 1 also inhibited the CO2 dependent O2 evolution and the flow of electrons from water to methylvi-ologen in spinach chloroplasts, and it inhibited the succinate-dependent O2 uptake in potato tuber mitochondria. Other phenanthrenes such as orchinol, which has a free hydroxyl at the 7-position, inhibit indole-3-acetic acid (lAA) oxidation catalyzed by horseradish peroxidase. 

Chloroplast and thylakold responses. In exploratory studies, all of the allelochemicals inhibited C02 dependent 0 evolution of intact spinach chloroplasts. values for the six representative... 

Reaction of 232 with 4-substituted l,3-oxazol-5(4/7)-one 247 led to diacylhydrazines 248 or to imidazole derivatives 249 depending on the reaction temperature (Scheme 24). l,2,4-Triazole-3-thione 250 was obtained by a two-step sequence from 232 with phenyl isothiocyanate and subsequent base-catalyzed cyclization of thiosemicarbazide 251. The effects of hydrazones 241-246 on inhibition of photosynthetic electron transport in spinach chloroplasts and chlorophyll content in the antialgal suspensions of Chlorella vulgaris were investigated <2005CEC622>. 

Cadmium (10 xm) inhibited C02 fixation of Chlorella pyrenoidosa by 62% (Hart and Scaife, 1977) a comparable decrease (74%) was found for spinach chloroplasts (Hampp et al., 1976). In-vivo external application of 450 pM cadmium reduced C02 fixation by only 34%, indicating that a large percentage of cadmium never reached the chloroplasts (Huang et al., 1974). 

Tricolorin A (46) and G (47) are prototype members of this class of amphiphilic glycoconjugates (24). They constitute the allelochemical principles of Ipomoea tricolor Cav., a plant used in traditional agriculture in Mexico as a cover crop to protect sugar cane against invasive weeds. Their molecular mechanism of action likely involves the inhibition of the FT-ATPase of the plasma membrane, an enzyme that plays a crucial role in plant cell physiology. Moreover, 46 acts as a natural uncoupler of photophosphorylation in spinach chloroplasts. This compound also displays general cytotoxicity against several... 

Aminoacid-tRNA synthetases were isolated from spinach chloroplasts by methods developed at Jealott s Hill. Cytoplasmic aaTRS s from carrot were isolated by standard procedures. Compounds were assayed as inhibitors of the chloroplastic aaTRS s at a single rate, 10 pM. The reaction was followed by phosphate generation and the percentage inhibition determined using literature methods. The IC50 value for the spinach chloroplastic enzymes and inhibition data for carrot cytoplasmic aaTRS s were determined for compounds of interest. All compounds were tested for post-emergence herbicidal activity, at 0.125, or at 0.5, or at 2.0 k a in standard screens." ... 

Table 1 Percentage inhibition of a range of spinach chloroplast aaTRS s by sulfamoyladenosines at lOpM (ND = Not Determined, LTRS = leucyl-tRNA synthetase, ITRS = isoleucyl-tRNA synthetase, VTRS = valyl-tRNA synthetase, ATRS = Alanyl-tRNA synthetase, GTRS = glycyl-tRNA synthetase)...

Compound Intended Tai et Percentage Inhibition of Spinach Chloroplast aaTRS s at 10 pM inhibitor concentration ... 

IC50 values were determined for selected compounds against the appropriate aaTRS from both spinach chloroplast and carrot cell cytoplasm (Table 2). No differentiation in potency was observed for inhibition of the chloroplastic, i.e. prokaryotic, and cytoplasmic, i.e. eukaryotic, enzymes. Enzymes from both tissues were equally susceptible to inhibition by the appropriate aminoacyl compound at nanomolar concentrations. Even closely related aminoacyl-sulfamoyladenosines were much weaker inhibitors, e.g. the leucyl derivative Ig and dealanylascamycin, la, were several orders of magnitude less potent than the appropriate aminoacyl-sulfamoyladenosines, compounds le and If, versus ITRS. 

H Baltscheffsky (1963) Inhibition of photophosphorylation in isolated spinach chloroplasts by lower aliphatic straight-chain alcohols. Acta Chem Scand 17 (supp.1) 308-312... 

Aguilar, M. L Romero, M. G. Chavez, M. L King-Diaz, B. Lotina-Hermsen, B., Biflavonoids isolated from Selaginella lepidophylla inhibit photosynthesis in spinach chloroplasts, J. Agric. Food Chem., 2008, 56, 6994-7000. 

Mishra NP, Mishra RK and Singhal GS (1993) Involvement of active oxygen species in photoinhibition of Photosystem II protection of photosynthetic efficiency and inhibition of lipid peroxidation by superoxide dismutase and catalase. J Photo-chem Photobiol B Biol 19 19-24 Miyake C and Asada K (1992) Thylakoid-bound ascorbate peroxidase in spinach chloroplasts and photoreduction of its primary oxidation product monodehydroascorbate radicals in thylakoids. Plant Cell Physiol 33 541-553 Miyake C and Asada K (1994) Ferredoxin-dependent photoreduction of the monodehydroascorbate radical in spinach thylakoids. Plant Cell Physiol 35 539-549 Miyake C, Schreiber U, Hermann H, Sano S and Asada K (1996) Monodehydroascorbate radical reductase-dependent photoreduction of oxygen in chloroplast thylakoids. Plant Cell Physiol 37 s284... 

Figure 1. Representative traces of absorbance changes that show inhibition by dinoseb of valinomycin-induced swelling of intact spinach chloroplasts (B), spinach thylakoids (C), and mung bean mitochondria (D) suspended in isotonic KSCN. The model system is presented diagrammatically in A. Swelling was initiated by the addition of 0.1 /xM valinomycin (VAL),...

Inhibition of valinomycin-induced swelling of intact spinach chloroplasts, spinach thylakoids, and mung bean mitochondria by FCCP, selected herbicides, and carbanilates. 

Binding Events Modeled with Quantum Chemical Descriptors. Inhibition of the Hill reaction (spinach chloroplasts) correlates with the energy level of the highest occupied MO on amide nitrogen for a series of piperldinoacetanilides (139). Electron density on amide nitrogen also correlates well with E,... 

Little is known on the biological activities of C. a. because it is difficult to obtain adequate amounts of the pure substances. Apart from weak antibiotic activities, membrane effects (ionophoric) on mitochondria have been reported and an inhibition of phosphorylation in isolated spinach chloroplasts has been demonstrated. Ut. Hegnauer VI, 65-68 IX, 353-358 Manske 15, 165-205 Nachr. Chem. Techn. Lab. 37,1034-43 (1989) (review) Nat. Prod. Rev. 14, 75 (1997) (review) Pelletier 3, 113-168 Tetrahedron Lett. 39, 283 (1998) (synthesis zizyphine) 40, 83, 455 (1999) Zechmeister 75, 1 -179 (review). -[HS 2939901... 

Both DIMBOA and DIMBOA glucoside inhibit photo-phosphorylation by spinach chloroplasts (Queirolo et al., 1981). DIMBOA is a potent inhibitor of cyanide-insensitive respiration in potato mitochondria (Hediger and Seigler, unpublished data). 

In this connection it is interesting to realize that tricolorin A was also shown to uncouple photophosphorylation in spinach chloroplasts in a potent manner (Ujj = 0.33 jM) and to inhibit - in high concentrations (20pM) - electron transport in photosystem II. Again the intact macrolactone moiety turned out to be cmcial (Achnine et al. 1999). Glycoresins might be useful as leads for new herbicides (Vyvyan 2002). 

Pyrenocine A has bimodal effects on onion root and spinach chloroplast lipid metabolism. Low concentrations and shorter preincubation periods promote lipid synthesis from 14C-acetate while high concentrations and longer preincubation periods inhibit lipid synthesis. Maximum stimulation of lipid synthesis (approximately 75%) was observed when onion roots were preincubated for. 5 h with 25 Aig/ml pyrenocine A while maximum inhibition (approximately 80%) was observed when onion roots were pretreated with 100 ug/ml pyrenocine A for 24 h (Tables 1 and II). Over the range of onion treatments with pyrenocine A, there was a marked increase in the proportions of glycerolipid synthesized at the expense of sterols (50%... 

In jojoba and spinach chloroplasts oxygen evolution was maximum (120 ymol O2 h- mg" Chi) at 25 C. From 25 C to 40 C the oxygen evolution slightly decreased up to 66-68% of the initial activity. At higher temperatures a rapid drop of the O2 evolved occurred and led to a total inhibition at 47.5 C for spinach and at 52.5°C for jojoba. 

Table I demonstrates that when isolated spinach chloroplasts are incubated with 35sO - in darkness there is low incorporation into SQDG. The incorporation can be increased by addition of ATP or by illumination. Neither ADP nor AMP significantly improves incorporation in darkness. While ATP stimulates incorporation in illuminated chloroplasts, ADP and AMP inhibit the incorporation. One might expect that the first...

Arnon and his collaborators (11,15) have reported that whole spinach chloroplasts, prepared in 0.5 M glucose or 0.35 M NaCl, are able to carry out not only the Hill reaction (f.c., the photolysis of water in the presence of artificial hydrogen acceptors) but also photosynthetic phosphorylation and carbon dioxide fixation. Both these processes are light-dependent and strongly inhibited by o-phenanthroline, which interferes with the photochemical reaction. Their early results are shown in Table V. These important findings... 

Later experiments by Willemot and co-workers confirmed these conclusions. In addition, these authors noticed that spinach leaves were relatively unaffected by Sandoz 9785. By contrast, disks from spinach leaves were sensitive, perhaps because in leaves there was a detoxification process. Isolated spinach chloroplasts were insensitive to Sandoz 9785, and it was suggested that this might be due to a need for Sandoz 9785 to be activated before it could inhibit A15-desaturation. ... 

Substituted 2-anilino-l,3,4-thiadiazoles inhibit oxidative phosphorylation (in rat liver mitochondria) and photosynthetic phosphorylation (in spinach chloroplasts). ... 

The numbers calculated for the apparent Km(ADP) values, determined in the presence of 1 mM MgCl2 from Lineweaver-Burk plots revealed through their linear appearance that the velocity of the reaction was a function of ADP concentrations. This implies only one active absorption site for ADP on the enzyme by the substrate Mg-ADP as it has been concluded for spinach chloroplasts by Murakami and Strotmann (1978). The adenylate kinases were sensitive to AMP which functioned as an product inhibitor, as expressed by the obtained K (AMP) values, and ADP exhibited a substrate inhibition effect indicated by the Ki(ADP) values obtained (Table 2). DAPP likewise functioned as a competitive inhibitor in rather low concentrations (Table 2) in contrast to its action in beef heart mitochondria (Tomasselli and Noda, 1980). 

Barr R and Crane FL (1982) Ca and calmodulin antagonists inhibit the proton gradients associated with non-cyclic and cyclic photophospho-rylation in spinach chloroplasts, Biochem. Biophys. Res. Commiin. 

Oliver D and Jagendorf AT (1976) Inhibition of the Coupling Factor from Spinach Chloroplasts by Trinitrobenzenesulfonic acid. Fed. Proc. 2, 596. 

Barr R, Troxel KS and Crane FL (1982) Calmodulin antagonists inhibit electron transport in photosystem II of spinach chloroplaSts,Biochem. Biophys. Res. Commun. 104, 1182-1188... 

---