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1.
Scavenging of Hydrogen Peroxide in Prokaryotic and Eukaryotic Algae: Acquisition of Ascorbate Peroxidase during the Evolution of Cyanobacteria 总被引:4,自引:0,他引:4
Ascorbate (AsA) peroxidase was found in six species of cyanobacteriaamong ten species tested. Upon the addition of H218O2 to thecells of AsA peroxidase-containing cyanobacteria, 16O2 derivedfrom water and 18O2 derived from H2I8O2 were evolved in thelight. The evolution of 16O2 was inhibited by DCMU and did notoccur in the dark, but I8O2 was evolved even in the dark orin the presence of DCMU. Similar light-dependent evolution of16O2 was observed in the cells of AsA peroxidase-containingEuglena and Chlamydomonas. However, the cells of AsA perox-idase-lackingcyanobacteria evolved only 18O2 in either the light or dark.Furthermore, the quenching of chlorophyll fluorescence inducedby hydrogen peroxide was observed only in the cells of the AsAperoxidase-containing Synechocystis 6803, and not in the cellsof Anacystis nidulans which lacks AsA peroxidase. Thus, cyanobacteriacan be divided into two groups, those that has and those thatlacks AsA peroxidase. The first group scavenges hydrogen peroxidewith the peroxidase using a photoreductant as the electron donor,and the second group only scavenges hydrogen peroxide with catalase. (Received July 23, 1990; Accepted October 18, 1990) 相似文献
2.
The functional pool size of electrons in the intersystem chainof the chloroplasts of maize was estimated to be about 25 perP700 by the redox change in P700 with single- and multiple-turnoverlights under far-red light in intact leaves. This is about twicethe pool size observed in C3 plants. Furthermore, the stromalpool size of electrons that can be donated to P700+ after actinicillumination was larger in maize leaves than in leaves of C3plants, giving a maximum value of 225 electrons per P700. Maizeleaves showed an increase in the yield of modulated Chl fluorescenceafter turning off of actinic light, which confirms the donationof electrons in the dark to the intersystem chain from the stromaldonors that accumulated during actinic illumination. We proposethat the mesophyll chloroplasts are responsible for a high levelof electron-donating activity to the intersystem chain fromstromal donors such as triose phosphates and malate with NADPHas an intermediate. The level of P700+ under strong far-redlight was decreased after actinic illumination, suggesting theoperation of an actinic light-triggered cyclic electron flowin chloroplasts of the bundle sheath cells. (Received August 14, 1992; Accepted October 13, 1992) 相似文献
3.
Junichi Mano Kunio Kawamoto G. Charles Dismukes Kozi Asada 《Photosynthesis research》1993,38(3):433-440
A new binding site for anions which inhibit the water oxidizing complex (WOC) of Photosystem II in spinach has been identified. Anions which bind to this site inhibit the flash-induced S2/S0 catalase reaction (2H2O22H2O+O2) of the WOC by displacing hydrogen peroxide. Using a mass spectrometer and gas permeable membrane to detect the 32O2 product, the yield and lifetime of the active state of the flash-induced catalase (to be referred to simply as flash-catalase) reaction were measured after forming the S2 or S0-states by a short flash. The increase in flash-catalase activity with H2O2 concentration exhibits a Km=10–20 mM, and originates from an increase in the lifetime by 20-fold of the active state. The increased lifetime in the presence of peroxide is ascribed to formation of the long-lived S0-state at the expense of the unstable S2-state. The anion inhibition site differs from the chloride site involved in stimulating the photolytic water oxidation reaction (2H2OO2+4e-+4H+). Whereas water oxidation requires Cl- and is inhibited with increasing effectiveness by F-CN-N3
-, the flash-catalase reaction is weakly inhibited by Cl-, and with increasing effectiveness by F-CN-, N3
-. Unlike water oxidation, chloride is unable to suppress or reverse inhibition of the flash-catalase reaction caused by these anions. The inhibitor effectiveness correlates with the pKa of the conjugate acid, suggesting that the protonated species may be the active inhibitor. The reduced activity arises from a shortening of the lifetime of the flash-induced catalase active state by 3–10 fold owing to stronger anion binding in the flash-induced states, S2 and S0, than in the dark S-states, S1 and S-1. To account for the paradoxical result that higher anion concentrations are required to inhibit at lower H2O2 concentrations, where S2 forms initially after the flash, than at higher H2O2 concentrations, where S0 forms initially after the flash, stronger anion binding to the S0-state than to the S2-state is proposed. A kinetic model is given which accounts for these equilibria with anions and H2O2. The rate constant for the formation/release of O2 by reduction of S2 in the WOC is <0.4 s-1.Abbreviations ADRY
acceleration of the deactivation reactions of the water splitting enzyme system Y
- BTP
bis [tris(hydroxymethyl)methylamino]-propane
- CCCP
carbonylcyanide m-chlorophenylhyrazone
- DCBQ
2,5-dichlorobenzoquinone
- DMBQ
2,3-dimethylbenzoquinone
- WOC
water oxidizing complex 相似文献
4.
Thylakoids from mesophyll cells of maize showed a high rateof the ferredoxin (Fd)-dependent and antimycin A (AntiA)-sensitivecyclic electron flow as determined by the quenching of 9-aminoacridinefluorescence which indicates the formation of 相似文献
5.
Suppression of Quantum Yield of Photosystem II by Hyperosmotic Stress in Chlamydomonas reinhardtii 总被引:1,自引:0,他引:1
Addition of ethylene glycol (EG) or NaCl to cells of Chlamydomonasreinhardtii induced transient non-photochemical quenching ofChl fluorescence correlated with the inhibition of photosyntheticoxygen evolution. The induction of the quenching and subsequentrecovery proceeded not only in the light but also in the dark.The quenching was almost unaffected by the protonophore nigericin,suggesting the involvement of a type of non-photochemical quenchingattributable to a state 2 transition. Higher concentrationsof EG or NaCl caused a delay of the recovery of the maximumfluorescence yield (Fm'). Dark reduction rate of P700+ afterthe application of a flash light in the presence of DCMU wasenhanced by the hyperosmotic shock, suggesting a stimulatedreduction of the intersystem electron carriers. It is proposedthat the osmotic stress stimulates electron donation from stromalcomponents via the NAD(P)H dehydrogenase, which results in thereduction of the intersystem chain and triggering of a state2 transition leading to stimulated cyclic PSI activity. (Received May 16, 1995; Accepted July 26, 1995) 相似文献
6.
Monodehydroascorbate Reductase in Spinach Chloroplasts and Its Participation in Regeneration of Ascorbate for Scavenging Hydrogen Peroxide 总被引:15,自引:0,他引:15
The primary reaction product of chloroplast ascorbate peroxidaseactivity was shown to be monodehydroascorbate radical (MDA).MDA reductase (EC 1.6.5.4
[EC]
) was localized in spinach chloroplaststroma. The MDA reductase activity of spinach chloroplasts,using NAD(P)H as electron donor, could account for the regenerationof ascorbate from MDA produced by ascorbate peroxidase activity.In the absence of MDA reductase, MDA disproportionated to ascorbate(AsA) and dehydroascorbate (DHA). The DHA was reduced to AsAby DHA reductase (EC 1.8.5.1
[EC]
) in chloroplasts. Both NADH andNADPH served as the electron donor of partially purified MDAreductase from spinach leaves. (Received September 24, 1983; Accepted January 23, 1984) 相似文献
7.
Kunshan Gao Yusho Aruga Kozi Asada Toshiaki Ishihara Toru Akano Masataka Kiyohara 《Journal of applied phycology》1991,3(4):355-362
Leafy thalli of the red algaPorphyra yezoensis Ueda, initiated from conchospores released from free-living conchocelis, were cultured using aeration with high CO2. It was found that the higher the CO2 concentration, the faster the growth of the thalli. Aeration with elevated CO2 lowered pH in dark, but raised pH remarkably in light with the thalli, because the photosynthetic conversion of HCO 3 ? to OH? and CO2 proceeded much faster than the dissociation of hydrated CO2 releasing H+. Photosynthesis of the alga was found to be enhanced in the seawater of elevated dissolved inorganic carbon (DIC, CO2 + HCO 3 ? + CO 3 ? ). It is concluded that the increased pH in the light resulted in the increase of DIC in the culture media, thus enhancing photosynthesis and growth. The relevance of the results to removal of atmospheric CO2 by marine algae is discussed. 相似文献
8.
Target analysis of the PS II reaction in spinach thylakoidsshowed that the respective molecular masses of the catalyticunits for oxygen evolution and the reaction center are about120 kDa and 250 kDa based on a kinetic separation of the tworeaction rates. The size of the oxygen-evolving enzyme agreedwith that determined for the PS II preparation from a thermophiliccyanobacterium by the same means [Nugent and Atkinson (1984)FEBS Lett. 170: 89]. Single hit-inactivation of oxygen evolutionand the PS II reaction center units indicates that each functionis driven by a structurally assembled unit. (Received August 6, 1984; Accepted December 17, 1984) 相似文献
9.
Kozi Asada 《Bioscience, biotechnology, and biochemistry》2013,77(8):1659-1660
Acidic heteropolysaccharides, d-glucurono-d-xylo-d-mannans were isolated from the water- and alkaline extracts of the fruit body of Tremella fuciformis Berk. Similar polysaccharides were isolated from the growing culture of the haploid cells of two strains (T–19 and T–7) of T. fuciformis, when they were cultured in sucrose or glucose-yeast extract medium. The extracellular polysaccharides contain, d-glucuronic acid, d-xylose and d-mannose [molar ratios, 1.3: 1.0: 3.5 (T–7) and 0.8: 1.0: 2.1 (T–19)], and, in addition, small proportions of l-fucose and O-acetyl groups. Methylation and Smith degradation studies indicated that both fruit body and extracellular polysaccharides are built up of α-(1 → 3)-linked d-mannan backbone chain to which β-linked d-glucuronic acid and single or short chains of β-(1 → 2)-linked d-xylose residues are attached at the C–2 position. l-fucose residues in the extracellular polysaccharides may form the single branches. The structural features of these polysaccharides are discussed in comparison with the similar polysaccharides from other fungi. 相似文献
10.
Atsumi Kamogawa Kozi Yokobayashi Toshio Fukui 《Bioscience, biotechnology, and biochemistry》2013,77(12):2813-2819
Maltose phosphorylase (EC 2.4.1.8) from Lactobacillus brevis was purified 29-fold over the crude extract. The final preparation was at least 80% pure and had a specific activity of 18 units/mg protein. The molecular weights of the native enzyme and of the component dissociated in sodium dodecyl sulfate were 150,000 and 80,000, respectively. The enzyme does not contain pyridoxal-5′-phosphate as a cofactor. It can not act on maltitol, malto-triitol, sucrose, lactose and trehalose, and essentially not on isomaltose, maltobionic acid, maltotriose and maltotetraose. Inhibitory effect was observed with CuSO4, HgCl2 and p-chloromercuribenzoate. Some other properties were also examined. A possibility of using this enzyme for the analysis of maltose was proposed. 相似文献