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1.
  1. In the presence of NADP+ and Mg++, the bundle sheath strandsisolated from corn (Zea mays) leaves by cellulase treatmentsdecarboxylated malate in the light at an initial rate (200 µmoles/mgchl.hr), which was sufficient to account for photosyntheticCO2 fixation in intact leaves. This rate gradually slowed downand then stopped. The final level of the malate decarboxylatedwas approximately equal to the amount of NADP+ added.
  2. Rapidand continued decarboxylation of malate was observed whenNADP+,3-phosphoglyceric acid and ATP (and Mg++) were addedtogether.The addition of ADP instead of ATP showed a similareffect.Light did not show any effect on the malate decarboxylationin the presence of ATP or ADP.
  3. When malate was added to thebundle sheath strands in the presenceof exogenous NADP+ NADP+was rapidly reduced. The reductionstopped after 2 min when,73% of the added NADP+ was reduced.The further addition of3-phosphoglyceric acid and ATP broughtabout a decrease in theNADPH-level, which rose again to attaina new steady level.
  4. The transfer of radioactivity from (1-14C-3-phosphoglycericacid to dihydroxyacetone phosphate in the bundle sheath strandsin the presence of ATP and NADP+ was greatly enhanced by theaddition of malate.
  5. In the presence of ribose 5-phosphateand ATP, the rate of 14C-transferfrom (4-14C)-malate to theintermediates of the reductive pentosephosphate cycle was equalto that of 14CO2 fixation in the light.
All these results support the current view that in the bundlesheath cells of C4 plants belonging to the NADP-malic enzyme-group,the decarboxylation of malate is coupled to the fixation ofthe released CO2 and the reduction of 3-phosphoglyceric acidformed as a result of CO2 fixation. 1 Part of this research was reported at the 40th Annual Meetingof the Botanical Society of Japan Osaka, December, 1975. 3 Present address: Laboratory of Chemistry, Faculty of Medicine,Teikyo University, 359 Otsuka, Hachioji-City, Tokyo 173, Japan. (Received April 30, 1977; )  相似文献   

2.
  1. In the early stage of CO2-fixation by Thiobacillus thiooxidans,which was incubated aerobically in the presence of sulfur, mostpart of the fixed carbon was found in the phosphate ester fraction.
  2. The fixation was inhibited by NaF, picolinic acid, PCMB, azide,dipyridyl, o-phenanthroline, monoiodoacetic acid, and arsenite,each in the concentration range where the sulfur oxidation wasnot affected strongly.
  3. The crude extract of this organismcould fix CO2 in the presenceof ATP, R-5-P and Mg++. Most partof the fixed carbon was foundin PGA.
  4. The crude extract showedthe CO2-fixation coupled with the H2S-oxidationin the presenceof ADP.
  5. An appreciable reduction of PGA could not be detectedin thepresence of reducing systems, involving TPNH and DPNH.
(Received March 6, 1962; )  相似文献   

3.
The effects of EDTA·Mg or GEDTA·Mg on the uptakeof nutrient ions, the release of Ca++ and nucleotides into themedium and the nucleic acid contents in rice and red bean rootswere investigated.
  1. Both EDTA and EDTA·Mg induced similarly the release ofCa from roots.
  2. EDTA·Mg as well as EDTA brought abouta significant repressionin K uptake, but had an insignificantor no effect on P, NH4and NO3 uptakes. EDTA·Ca did notrepress K, P, NH4 andNO3 uptakes.
  3. EDTA or GEDTA acceleratedthe degradation of nucleic acid andthe release of nucleotides,while EDTA·Mg or GEDTA·Mghad no such effect.
These results indicate that the indispensable role of intracellularCa in K uptake does not appear to be directly associated withRNA metabolism. (Received July 29, 1965; )  相似文献   

4.
  1. Formyltetrahydrofolate synthetase (E. C. 6. 3. 4. 3) was foundto be widely distributed in higher plants and the high enzymeactivity was observed in green leaves of Brassica and Alliumspecies, spinach, and in pea seedlings. In pea seedlings, theenzyme activity changed during the course of germination, andmost of the enzyme activity was located in a soluble fractionof the cytoplasm.
  2. The enzyme was labile and lost the activityrapidly, even whenstored at 5 in the presence of 0.1 M mercaptoethanol.It was,however, found that ammonium sulfate was very effectivein stabilizingthe enzyme activity.
  3. The enzyme has been purifiedapproximately 500-fold from extractsof pea seedlings by treatmentswith ammonium sulfate, protaminesulfate, hydroxylapatite, calciumphosphate gel, and DEAE-cellulosecolumn chromatography.
  4. Thepurified enzyme was specific for formate, ATP and FAH4,andthe Michaelis constants for these reactants were 2.1 10–2M, 5.1 10–4 M, and 5.6 10–3 M, respectively.
  5. The optimum pH was found to be 8.0, and the optimal temperaturewas observed at 37. Both NH4$ and a divalent cation (MgSS orMnSS) were required for the optimal activity.
1 Studies on the Enzymatic Synthesis and Metabolism of FolateCoenzymes in Plants. II. (For the previous paper see reference(8)) A part of this paper was presented at the Meeting of theKansai Division of the Agricultural Chemical Society of Japan,Kyoto, January 29, 1966.  相似文献   

5.
  1. It has been established that the absence of isocitric dehydrogenaseactivity in cotyledons of Vigna sesquipedalisin the germinationstage is due to the lack of endogenous TPN. It is unlikely thatthe TCA cycle in the cotyledon is operative.
  2. The activitiesof enzymes of the glyoxylate cycle, a modifiedTCA cycle, weremeasured through the germination stage. Theiractivities wereconsiderably higher in the cotyledon tissuethan in the hypocotyl.A dominant metabolic pathway of isocitricacid in the cotyledonmay be the glyoxylate cycle.
  3. DPN kinase which produces TPNfrom DPN, ATP and Mg++ was localizedin the supernatant portionof cell components in the cotyledon.Its activity was low. DPNkinase serves as a control factorfor the cotyledon metabolism.
(Received April 17, 1961; )  相似文献   

6.
  1. Reduction of nitrate, nitrite and hydroxylamine by intact cellsof Anabaena cylindrica was investigated with special referenceto the stimulating effect of light on these processes.
  2. Itwas found that in light and under anaerobic condition thesecompounds are reduced to ammonia, with the production of extraoxygen. The stoichiometry of the reactions under these conditionscan be represented as follows: HNO2+H2O=NH2+2O2 HNO2+H2O=NH2+1O2 NH2OH+H2O=NH2+O2+H2O
  3. Reduction of nitrite and hydroxylaminewas markedly suppressedby CMU in the light but not in the dark.KCN inhibited reductionto the same extent both in the lightand in the dark. Reductionin the light was much less sensitiveto the uncoupling agent,DNP, than was that in the dark.
  4. Atlow light intensities, CO2– was suppressed by 20–30per cent by the simultaneous provision of nitrite, but the nitritereduction was not affected at all by CO2. At high light intensities,reduction of nitrate and nitrite was considerably acceleratedby CO2
  5. On the basis of these findings, a possible mechanismfor thelight stimulation of the reactions in question was brieflydiscussed.
(Received August 22, 1962; )  相似文献   

7.
The activity of shikimate: NADP oxidoreductase [EC 1. 1. 1.25] in sweet potato root tissue increased soon after slicing.Enzyme preparations obtained from both sliced tissue and fromfresh tissue probably contained a single enzyme component, andthey showed identical chromatographical behaviour. Km values of the enzyme for NADP and shikimate were 1.0x10–4Mand 1.3 x 10–3M, respectively. Enzyme activity was potentlyinhibited by SH-inhibitors such as p-chloromercuribenzoate andoxidized glutathione. Enzyme activity was affected neither by mononucleotides suchas ATP, ADP and AMP, divalent cations, Mg++, Ca++ and Mn++,nor by metabolites such as tryptophan, phenylalanine, tyrosineand t-cinnamic acid which are involved in aromatic compoundsyntheses. The enzyme rapidly lost its activity. This inactivation reactionshowed a time course consisting of two steps of the first-orderreaction. The inactivated enzyme preparation was not reactivatedby thiol compounds such as cysteine, 2-mercaptoethanol and glutathione,although these reagents, to a certain extent, protected theenzyme from inactivation. The results suggest that denaturationof the enzyme protein was involved in inactivation of the enzyme. 1Part 74 of the phytopathological chemistry of sweet potatowith black rot and injury. 2Present address: Department of Biology, Faculty of Science,Tokyo Metropolitan University, Setagaya-ku, Tokyo. (Received August 5, 1968; )  相似文献   

8.
Metabolic control within skeletal muscle is designed to limit ADP accumulation even during conditions where ATP demand is out of balance with ATP synthesis. This is accomplished by the reactions of adenylate kinase (AK; ADP+ADP AMP+ATP) and AMP deaminase (AMP+H2O NH3+IMP), which limit ADP accumulation under these conditions. The purpose of this study was to determine whether AK deficiency (AK–/–) would result in sufficient ADP accumulation to be visible using 31P-NMRS during the high energy demands of frequent in situ tetanic contractions. To do this we examined the high-energy phosphates of the gastrocnemius muscle in the knockout mouse with AK1–/– and wild-type (WT) control muscle over the course of 64 rapid (2/s) isometric tetanic contractions. Near-complete depletion of phosphocreatine was apparent after 16 contractions in both groups. By 40 contractions, ADP was clearly visible in AK1–/– muscle. This transient concentration of the NMR visible free ADP was estimated to be 1.7 mM, and represents the first time free ADP has been directly measured in contracting skeletal muscle. Such an increase in free ADP is severalfold greater than previously thought to occur. This large accumulation of free ADP also represents a significant reduction in energy available from ATP, and has implications on cellular processes that depend on a high yield of energy from ATP such as calcium sequestration. Remarkably, the AK1–/– and WT muscles exhibited similar fatigue profiles. Our findings suggest that skeletal muscle is surprisingly tolerant to a large increase in ADP and by extension, a decline in energy from ATP. muscle energetics; muscle relaxation; magnetic resonance spectroscopy  相似文献   

9.
Some enzymic Properties of a partially purified preparationof sucrose phosphate synthetase (E.C.2.4.1.14) from germinatingrice seed scutella were studied. Examination of the reactionkinetics revealed that the rate of synthesis of sucrose phosphatefollows the Michaelis-Menten equation at an optimum PH of 7.5,having Km of 25 mM for UDP-glucose, and of 4.9 mM for fructose6-phosphate. UDP inhibited the enzyme reaction competitively;K1 of 3.3 mM. Fe++ and Fe+++ activated the enzyme reaction about2-fold; Ka, 0.3 mM and 2.0 mM, respectively. Co++, Co(NH3)6+++,Mg++ and Mn++ also activated the enzyme reaction. At high concentrationK+ activated the enzyme reaction with the maximum activationof 24% at 400 mM. The molecular weight and S20,w value of theenzyme were determined as 4.5 ? 105 and 10.4S, respectively. 1Part IV of this series is Ref. (5). 2California Foundation for Biochemical Research Fellow (1973). (Received December 20, 1973; )  相似文献   

10.
  1. The effect of -hydroxy sulfonates and sulfite, inhibitors ofglycolate oxidase, on the photochemical reactions of spinachchloroplasts was studied. The photo reduction of ferricyanideand NADP was not affected by the poisons, whereas the photophosphorylationand 14CO2 fixation were inhibited.
  2. Glyoxylate was photoreducedby the chloroplasts in the presenceof PPNR and glyoxylate reductase,and this reduction was acceleratedby the addition of NADP.ATP formation accompanied with thereduction of glyoxylate bythe illuminated chloroplasts wasobserved. It is supposed thatglyoxylate oxidizes the photoreducedNADPH2 or PPNR and thusthe photophosphorylation is stimulated.
1A part of this paper was presented at the annual meeting ofAgricultural Society of Japan, in August, 1964. 2Present address: Radiation Center of Osaka Prefecture, Sakai,Osaka.  相似文献   

11.
Sugar beet and spinach beet were grown in sand culture withdifferent sources of nitrogen or iron and different levels ofmolybdenum and heavy metals. Chlorophyll and some magnesiumfractions were determined. Extra molybdenum accentuated chlorosis caused by excess of Mn++,Cr+++, Zn++, and Cu++ and decreased it in the presence of CrO4––with nitrate. In the presence of these ions urea reduced chlorophyll in youngand increased it in old leaves of sugar beet. Effects of ureaand molybdenum were additive and independent. Ammonium sulphatecaused increased chlorosis of spinach beet with Mn++ and Zn++. The existence of an acetone-soluble magnesium fraction otherthan chlorophyll was shown. Excess Cu++ and Zn++ decreased totalmagnesium; Mn++ did not. Mn++ and Zn++ reduced chlorophyll,increased the non-chlorophyll acetone-soluble magnesium, butreduced other fractions. Ferrous iron ipcreased total magnesiumcontent and also increased the acetone-soluble fractions inthe presence of Mn++ and Zn++. Extra molybdenum decreased theacetone-soluble magnesium fractions but did not affect the totalmagnesium content. Significant interactions between Mo, N, Fe, and heavy metalswere also disclosed.  相似文献   

12.
The luciferin-luciferase method was used to determine ATP extractedfrom darkmaintained and light-exposed samples of the green algaChlorella pyrenoidosa and of the blue-green alga Anacystis nidulans.A few measurements on Synechococcus lividus (a bluegreen thermophile,clone 65?C) are also reported.
  1. The light-minus-dark ATP levels (ATP) from aerobic cells ofChlorella and Anacystis were negative; however, ATP from Synechococcuswas positive. Large positive ATP was obtained in regularly grown(RG: moderate light) Chlorella treated with oligomycin; darklevels were reduced, light levels remained essentially unaffected.In high-light exposed (HLE) Chlorella, oligomycin reduced bothlight and dark ATP levels, but positive ATP was still obtained.However, in Anacystis, which has a different organization ofthylakoid membrane, oligomycin severely reduced both the lightand the dark ATP levels and the ATP remained negative.
  2. Theoligomycin (12 µM) treated Chlorella and the untreatedAnacystis and Synechococcus show the presence of cyclic photophosphorylationunder conditions in which the non-cyclic electron flow fromphotosystem II to photosystem I is blocked by 10 µM 3-(3,4-dichlorophenyl)-l,l-dimethylurea(DCMU), or not allowed to operate by the absence of CO2. Cyclicphotophosphorylation ranged from 10–30% of the maximumATP in RG, to 40–50% in HLE Chlorella. In RG Chlorella,cyclic and non-cyclic (in the absence of DCMU) photophosphorylation(ATP) saturate at about 103 ergs cm–2 sec–1 and104 ergs cm–2 sec–1 and 104 ergs cm–2 sec–1red (>640 nm) light, respectively; a lag was observed inthe light curve.
  3. In Chlorella, the addition of the photosystemI electron acceptormethyl viologen (MV; 1 mM) increased ATPby twofold. Furtheraddition of DCMU (25 µm) reduced thisto the level observedwith DCMU alone. If 1 mM reduced dichlorophenolindophenol orphenazine methosulphate (DCPIPH2 or PMSH2, respectively)wasadded along with DCMU, the ATP level was 30–40% ofthecontrol. Further addition of MV increased the JATP to be70–80%of that of the control. These and other resultsconfirm thepresence of both non-cyclic and cyclic photophosphorylationin vivo, the former predominating in Chlorella, and the latterin Anacystis and Synechococcus.
(Received May 1, 1973; )  相似文献   

13.
  1. The growth rate of cultured free-cells and their contents ofchlorophyll, Mg, K and N reached peaks on media containing Mn+= 60 and 80 meq per liter, or in which salts=2.7 and 3.6 atm.These concentration levels in the media were considerably higherthan those (Salts=1.5–2.0 atm) which produced good growthof intact plants. This discrepancy in media concentrations maybe due to differences in the culture conditions and in the morphologyof the materials.
  2. Very low Ca2+/(Mn+–Ca2+) equivalentratios of 0.1 to 0.01in a medium were sufficient for good growthof free cells, whilegenerally about unity of the ratio is requiredin a medium forgood growth of intact plants. The differencein the medium compositionmay also be due to morphological differencesin the materials.
  3. Addition of Cl to the medium furtherpromoted the growthrate and friability of cell clumps.
  4. Alow concentration of 0.01 mM BO33– in the medium alsopromoted the friability of cell clumps.
(Received August 15, 1972; )  相似文献   

14.
Tobacco RuDP carboxylase is completely soluble in 0.07 M NaClor 0.01 M Na2SO2, but is almost completely insoluble in salt-freesolutions at 40°C; the solubility seeming to depend on ionicstrength. Lowering the temperature increased solubility of theprotein. The solubility in 0.01–0.04 M NaCl at 0°Cwas more than double that at 40°C. RuDP solubilized theprotein even in a salt-free medium. The protein became insolubleagain on the addition of various divalent cations. Effectivenessof the metal ions was Zn++> Ni++>Co++>Mn++>Mg++>Ca++.Although most of the metal ions inhibited (Mg++ activated) enzymeactivity, no direct correlation was found between the degreeof solubility depression and the degree of enzyme inhibition. (Received October 4, 1971; )  相似文献   

15.
Intact chloroplasts (about 70% Class I chloroplasts) isolatedfrom spinach leaves incorporated 150 nmoles of [1-14C] acetateinto fatty acids per mg chlorophyll in 1 hr at pH 8.3, 25°Cand 25,000 lux. On electron and phase-contrast microscopiescombined with hypotonic treatment of chloroplasts, this syntheticactivity was shown to be proportional to the percentage of ClassI chloroplasts in the preparation. Light was necessary for thesynthesis, the activity in the complete reaction mixture inthe dark being only 2% of that in the light. The synthetic activityincreased with increasing intensities of light to reach saturationat 6,000 lux. CoA and ATP were most effective as cofactors,HCO3, HPO42–, Mg2$ and Mn2$ were less effective.ATP could be replaced by ADP in the presence of Pi, suggestingpossible supply of ATP by photophosphorylation. Omission ofthe NADPH-generation system and NADH did not affect the synthesis,indicating sufficient provision of endogenous NADPH and NADHin intact chloroplasts under light. Addition of DTE did notcause recovery of the synthetic activity of intact chloroplastsin the dark. 1 Present address: Radioisotope Centre, University of Tokyo,Yayoi, Bunkyo, Tokyo 113, Japan. (Received August 26, 1974; )  相似文献   

16.
Macduff, J. H., Hopper, M. J., Wild, A. and Trim, F. E. 1987.Comparison of the effects of root temperature on nitrate andammonium nutrition of oilseed rape (Brassica napusL.) in flowingsolution culture. II. Cation-anion balance.—J. exp. Bot.38: 1589-1602. The effects of root temperature and form of N nutrition (NH4or NOJ) on the mineral composition of the plant, the balanceof inorganic cation-anion uptake and on the apparent net effluxof H +/OHions from the roots were studied with 49-d-oldoilseed rape (Brassica napusL. cv. Bien venu) in flowing solutionculture. Plants were pre-treated for 14 d at a root temperatureof 5 °C prior to constant root temperatures of 3, 7, 11or 17°C for 14 d, with a common shoot temperature of 20/15°Cday/night. Nitrogen was supplied as NH+44 or NO3 at 10mmol m3. Values of Q10 (7-17°C) for mean unit absorptionrates of all the major nutrient ions (K+ , Mg++ , NH+4, SO4,H2PO4, NO3), except Ca++, were > 2.0 over the first 5 d oftreatment but thereafter were < 1.5; the apparent effectof temperature on uptake rates diminished with time. Under NH+4nutrition, inorganic cation uptake (Mg+ + + K++Ca+ + +NH+4)exceeded inorganic anion uptake (SO44+ H2PO4) over 14d at all temperatures, with the proportion of cation uptakeas NH4 remaining constant (0.67-0-68) irrespective of root temperature.The net efflux of H + from the roots approximately balancedNH+4 uptake (1:1) over 14 d at each temperature and also balancedthe difference between the total uptake of inorganic cationsand inorganic anions. Under NO3 nutrition, the sum of the netefflux of OH and the change in the carboxylate contents of plantsover 14 d approximately balanced the sum of NO3 and SO4reduced in the plant. The majority of the negative charge associatedwith the reduction of NO3 and SO4 was apparently effluxedas OH, but this fraction was lower at low root temperatures.The results are discussed in terms of mechanisms that have beenproposed to regulate the internal pH of plants. Key words: Brassica napus, oilseed rape, root temperature, cation-anion balance, H+/OH efflux.  相似文献   

17.
The cytoplasmic [MgATP]/[ATP]free ratios, free Mg2+ concentrations,and phosphorylation potentials in mung bean [Vigna mungo (L.)Hepper] root tip cells were investigated by 31P nuclear magneticresonance spectroscopy. 31P NMR spectra show well defined peaksdue to G6P, cytoplasmic Pi, vacuolar Pi, ATP, UDP-glucose andnicotinamide adenine nucleotides. The concentrations of phosphorusmetabolites were determined from quantitative 31P NMR spectra.The [MgATP]/[ATP]free ratio was 9.45. Accordingly, about 90%of the cytoplasmic ATP was complexed to Mg2+. Utilizing thedissociation constant (Kd) determined for MgATP, the cytoplasmicfree Mg2+ concentration was estimated to be 0.4mM. The NMR-derivedphosphorylation potential, [ATP]/([ADP][Pi]), was 960 M-1. Thesodium azide treatment decreased the [ATP]/[ADP] ratio and thephosphorylation potential, and increased the [Mg2+]free. Metabolicinhibition may have been enhanced by an increase in [Mg2+freeand a decrease in the free energy change for ATP hydrolysis,which resulted due to a decrease in the ATP level. 1Present address: National Food Research Institute, TsukubaCity, Ibaraki 305, Japan. (Received February 8, 1988; Accepted June 1, 1988)  相似文献   

18.
  1. Hydrogen peroxide excretion by photosynthesizing intact spinachchloroplasts was determined. The rates were dependent on theoxygen concentration and on the ATP/NADPH requirement of thefinal electron acceptor. Upon CO2 assimilation a maximum rateof 0.9 µmol H2O2/mg chlorophyll/hr and half saturationat 7.5 x 10–5 M O2 were found. Excretion of H2O2 was considerablyreduced upon photosynthetic reduction of glycerate 3-phosphateor oxaloacetate.
  2. Light- and HCO3-saturated CO2 assimilationwas inhibited bymore than 50% by anaerobic conditions, whereuponquantum efficiencywas also drastically decreased. However,no anoxic influencewas detected with glycerate 3-phosphateas the terminal electronacceptor and the quantum requirementwith this acceptor wasnot increased by anaerobiosis. Thus theenhancing effect ofoxygen on CO2 assimilation was ascribedto an improvement ofphotosynthetic ATP supply.
  3. Since thestimulation of anaerobic photosynthetic CO2 assimilationbyoxygen was markedly greater than the concomitant increaseinH2O2 evolution, photosynthetic oxygen reduction alone isnotsufficient to produce the required additional ATP for theobservedenhanced CO2 assimilation. But it provides a meansto avoidthe over-reduction of photosynthetic electron carriersand thusenables aerobic cyclic photophosphorylation. This supportsthehypothesis that cyclic photophosphorylation is not an alternativeto ATP formation by "pseudocyclic" electron transport, but ratherthat it depends on the latter.
(Received January 5, 1981; Accepted March 9, 1981)  相似文献   

19.
Glycerol kinase is induced in cells ofPseudomonas aeruginosa strain PAO when grown in the presence of glycerol or glycerol-3-phosphate. The enzyme was isolated from the soluble cytoplasmic fraction of cell extracts and purified 500-fold by ammonium sulfate precipitation and chromatography on columns of Sephadex G-25, DEAE-Sephadex, hydroxyapatite, and Sephadex G-200. A molecular weight of 120,000 was estimated by gel filtration of the catalytically active enzyme. In polyacrylamide gel electrophoresis the purified product contained one major band of Coomassie Blue staining material. The enzyme exhibited an apparent Km of 40 M for glycerol and 23 M for ATP. Of the nucleotide triphosphates tested, only ATP served as a phosphoryl group donor. Mg++ or Mn++ was required for activity, although a threefold greater concentration of Mn++ was required when Mn++ substituted for Mg++. In contrast to most other catabolic glycerol kinases in bacteria, the enzyme was not inhibited by fructose-1,6-diphosphate nor by other tested metabolites.  相似文献   

20.
  1. A method was discovered for adapting the cells of Rhodospirillumrubrum to grow on a nitrate medium, a capacity initially lackingin the organism. The adapted cells were able to grow with nitrateas the sole source of nitrogen. The growth responses of theadapted cells towards various nitrogenous sources were investigatedunder various conditions of incubation (aero- and anaerobiosis,light and dark).
  2. The adapted cells were found to have simultaneouslyacquiredthe capacity for reducing nitrite and hydroxylamineas wellas nitrate. The path of nitrogen in the adapted cellswas assumedto be as follows: NO3 NO2 NH2OH CellularNitrogen.
  3. Nitrate metabolism of the adapted cells was investigatedundervarious conditions. In the light, nitrate was reducedand furtherassimilated, leaving insignificant amounts of nitritein themedium. In this case, consumption of nitrate was markedlyinhibitedby other forms of nitrogen (e.g., nitrite, hydroxylamine,aminoacids and ammonium salts). In the dark, nitrate was reducedas the terminal hydrogen acceptor in the oxidative breakdownof organic substances (e.g., malate) in the medium (i.e., nitraterespiration). More nitrite was accumulated in this case thanin the light. Molecular oxygen inhibited the reduction of, aswell as the growth on, nitrate in any of the above cases.
  4. Theeffects on the rate of nitrate reduction (and respiratoryoxygenuptake) caused by various experimental factors (pH, nitrateconcentration, electron donors, and addition of hydroxylamine)were investigated, using the resting cells of the adapted organism.
1 This paper was submitted to the University of Tokyo to fulfillthe requirement for the author's doctorate. 2 Present Address: Botanical Institute, Kyoto University, Sakyo-ku,Kyoto. (Received February 14, 1963; )  相似文献   

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