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1.
Earlier work has established that the saturable component ofuptake of RS-[214C]ABA by bean (Phaseolus coccineus L. cv. Prizewinner)root segments can be attributed to the action of a carrier.We now show that the carrier-mediated uptake is unaffected byRS-2-trans-ABA and lunularic acid and the unnatural R-ABA alsoappears to be ineffective. The specificity for S-ABA requiresthe halving of the Km value for ABA determined previously (2.6mmol m-3 for RS-; 1.3 mmol m-3 for S-ABA). The RS-1', 4'-cis-dioland RS-1'-deoxy ABA reduce the uptake of RS-[2-14C]ABA aboutas strongly as does unlabelled ABA, the K1 for 1'-deoxy ABAwas similar to the Km for ABA. The K1 for RS-1', 4'-trans-diolwas 15.7 mmol m-3. Consideration of the stereochemistry of thesecompounds suggests that the face of the ring of ABA away fromthe 1'-hydroxyl group interacts with the carrier site. Labelled material diffused out of undamaged root surfaces whichhad absorbed RS-[3H]ABA through an apical cut, suggesting thatABA is present in the apoplast. A simplified hypothesis is presented that can account for polartransport of ABA based on a gradient of a carrier in a tissuebut where the carrier is distributed uniformly on the apicaland basal ends of each cell. Key words: Uptake carrier, Abscisic acid, 1', 4'-Diol, Lunularic acid, Phaseolus coccineus, Polar-transport, Deoxyabscisic acid 相似文献
2.
The R- and S-enantiomers of racemic [2-14C]Me 1', 4'-cis-diolof abscisic acid have been separated by high performance liquidchromatography on an optically-active Pirkle column. R-[2-14C]-and S-[2-14C]abscisic acids, formed from the Me 1', 4'-cis-diolby oxidation and alkyline hydrolysis were fed to tomato shootsand the extracts analysed by reversed phase high performanceliquid chromatography. R-[2-14C]abscisic acid formed mainlythe abscisic acid glucose ester (ABAGE), abscisic acid l'-glucoside(ABAGS) and an uncharacterized conjugate. Dihydrophaseic acid4'-B-D-glucoside, the major metabolite of RS-abscisic acid intomato shoots, was found to be derived virtually exclusivelyfrom the natural, S-abscisic acid. Phaseic acid and conjugatesof abscisic acid were also found as products of the naturallyoccurring enantiomer. The resolution method was used to measurethe relative proportions of R and S enantiomers in the freeacid liberated from conjugates formed from RS-[2-14C]ABA fedto shoots. The ratios show an excess of the R-enantiomer: 5.8:1, ABAGE; 29.4: 1, ABAGE; 8.3: 1 for an uncharacterized conjugateand 6.1: 1 for the residual free [2-14C]ABA. Key words: ABA, HPLC, Tomato 相似文献
3.
Virkki Leila V.; Wilson Darren A.; Vaughan-Jones Richard D.; Boron Walter F. 《American journal of physiology. Cell physiology》2002,282(6):C1278
We havefunctionally characterized Na+-driven bicarbonatetransporter (NBC)4, originally cloned from human heart by Pushkin etal. (Pushkin A, Abuladze N, Newman D, Lee I, Xu G, and Kurtz I. Biochem Biophys Acta 1493: 215-218, 2000). Of the fourNBC4 variants currently present in GenBank, our own cloning efforts yielded only variant c. We expressed NBC4c (GenBank accession no.AF293337) in Xenopus laevis oocytes and assayed membrane potential (Vm) and pH regulatory function withmicroelectrodes. Exposing an NBC4c-expressing oocyte to a solutioncontaining 5% CO2 and 33 mM HCO elicited a large hyperpolarization, indicating that the transporter iselectrogenic. The initial CO2-induced decrease inintracellular pH (pHi) was followed by a slow recovery thatwas reversed by removing external Na+. Two-electrodevoltage clamp of NBC4c-expressing oocytes revealed largeHCO - and Na+-dependent currents. When wevoltage clamped Vm far from NBC4c's estimatedreversal potential (Erev), the pHirecovery rate increased substantially. Both the currents andpHi recovery were blocked by 200 µM4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS). We estimatedthe transporter's HCO :Na+ stoichiometryby measuring Erev at different extracellularNa+ concentration ([Na+]o)values. A plot of Erev againstlog[Na+]o was linear, with a slope of 54.8 mV/log[Na+]o. This observation, as well asthe absolute Erev values, are consistent with a2:1 stoichiometry. In conclusion, the behavior of NBC4c, which wepropose to call NBCe2-c, is similar to that of NBCe1, the firstelectrogenic NBC. 相似文献
4.
Abscisic acid (ABA) and 2-trans-ABA (t-ABA) biosynthesis werestudied in wild type Landsberg erecta and the three allelicaba mutants of Arabidopsis thaliana (L.) Heynh., which are impairedin epoxy-carotenoid biosynthesis. Labelling experiments with18O2and mass spectrometric analysis of [18O]ABA and its catabolitesABA-glucose ester (ABA-GE) and phaseic acid (PA), and t- ABAand t-ABA-GE, showed that t-ABA biosynthesis was less affectedthan ABA biosynthesis by mutations at the ABA locus. The aba-4allele caused the most severe impairment of ABA biosynthesiscompared with the other two mutant alleles aba-1 and aba-3,yet aba-4 plants synthesized as much t-ABA as wild type Landsbergerecta plants. Feeding experiments with RS- [2H6]ABA-aldehydeisomers and unlabelled xanthoxin isomers suggest that t-xanthoxinand t-ABA-aldehyde are precursors to ABA and t-ABA in Arabidopsis Key words: ABA-alcohol, ABA-aldehyde, ABA-glucose ester, 18O2 labelling, phaseic acid 相似文献
5.
The Metabolism of cis ABA-aldehyde by the Wilty Mutants of Potato, Pea and Arabidopsis thaliana 总被引:1,自引:0,他引:1
DUCKHAM S. C.; TAYLOR I. B.; LINFORTH R. S. T.; AL-NAIEB R. J.; MARPLES B. A.; BOWMAN W. R. 《Journal of experimental botany》1989,40(8):901-905
RS-[2H1] cis ABA-aldehyde was fed to ABA-deficient mutants ofpotato (droopy), pea (wilty) and Arabidopsis thaliana (aba1)along with appropriate non-mutant controls. Both the wilty andaba1 mutants readily oxidized the monodeuterated ABA-aldehydeto ABA. The incorporation of label into ABA by these two mutantswas indistinguishable from that detected in the non-mutant controls.In contrast, the droopy mutants poorly incorporated the labelledprecursor into ABA. Instead they reduced and isomerized RS-[2H1] cis ABA-aldehyde to a mixture of 2, cis and 2, trans ABA-alcohols.Thus the droopy mutant affects the last step in ABA biosynthesis,a position it shares with the tomato mutants, flacca and sitiens.Genetic evidence suggesting that droopy and sitiens may be correspondinggene loci is discussed. Key words: ABA metabolism, wilty mutants, pea, potato, Arabidopsis 相似文献
6.
Effects of Abscisic Acid on the Growth Pattern of the Shoot Apical Meristem and on Flowering in Chenopodium rubrum L. 总被引:1,自引:0,他引:1
Abscisic acid (ABA) at 1 x 104 M or 3 x 104 Mwas applied to the apical buds of Chenopodium rubrum plantsexposed to different photoperiodic treatments and showing differentpatterns of floral differentiation. Stimulation of growth inwidth of the apical meristem of the shoot and/or inhibitionof growth in length was obtained under all photoperiodic treatments.This change of growth pattern was followed by different effectson flowering. In non-induced plants grown under continuous light ABA stimulatedpericlinal divisions in the peripheral zone and the initiationof leaves as well as the growth in width of bud primordia. Inplants induced by two short days reduced growth of the meristemcoincided with ABA application. Longitudinal growth of the meristemwas inhibited in this case and only a temporary stimulationof inflorescence formation took place. In plants induced ata very early stage, ABA exerted a strong inhibitory effect onflowering. A permanent and reproducible stimulatory effect onflowering was obtained in plants induced by three sub-criticalphotoperiodic cycles if ABA was applied to apices released fromapical dominance. In this case formation of lateral organs andinternodes was promoted by ABA and was followed by stimulatedinflorescence formation. Gibberellic acid (GA2) at 1x 104M or 3 x 104 M brought about a similar effect on floweringas ABA, although the primary growth effect was different, i.e.GA2 stimulated longitudinal growth. The effects of ABA and GA2 on floral differentiation have beencompared with earlier results obtained from auxin and kinetinapplications. These growth hormones are believed to regulateflowering by changing cellular growth within the shoot apex.Depending on the actual state of the meristem identical growthresponses may result in different patterns of organogenesisand even in opposite effects on flowering. Shoot apex, flowering, photoperiodic induction, abscisic acid, gibberellic acid, Chenopodium rubrum L. 相似文献
7.
8.
Inhibition of Ion Transport in Excised Barley Roots by Abscisic Acid; Relation to Water Permeability of the Roots 总被引:4,自引:0,他引:4
Previous papers have shown that abscisic acid can inhibit transportof ions across the root to the xylem vessels, resulting in reducedexudation from excised roots or inhibiting guttation from intactplants. However, it has not been established whether the inhibitionwas due to a reduction in salt transport (Js) or in permeabilityof the roots to water (Lp). This paper investigates the effectof ABA on Lp and Js separately. It is shown that Lp increasedin ABA and then fell, but was about the same as in control rootswhen transport was inhibited. The effect of ABA on exudationtherefore appeared to be mainly due to reduction in Js. Inhibitionof Js was also present in intact, transpiring plants and sowas not due to reduced water flow. The inhibition of ion releaseto the xylem affected Na+, Mg2+, Ca2+, and phosphate as wellas the major ion in the exudate, K+. It is concluded that ABAinhibits salt transport to the shoot by acting on ion transportinto the xylem, and not by reducing water flow coupled withsalt transport. 相似文献
9.
A Cyt P450 (P450C4H) possessing trans-cinnamate 4-hydroxylase(C4H) activity was purified to apparent homogeneity from microsomesof etiolated mung bean seedlings. Upon SDS-polyacrylamide gelelectrophoresis, the purified preparation gave a single proteinband with a molecular mass of 58-kDa. Its specific P450 contentwas 12.6 nmol (mg protein)1. Using NADPH as electrondonor, purified P450C4H aerobically converted trans-cinnamicacid to p-coumaric acid with a specific activity of 68 nmolmin1 nmol1 P450 in a reconstituted system containingNADPH-Cyt P450 reductase purified from the seedlings or rabbitliver microsomes, dilauroyl phosphatidylcholine, and cholate.This specific activity is by far the highest for reconstitutedC4H systems so far reported and provides direct evidence thatC4H activity is actually associated with a P450 protein. Inthe oxidized state P450C4H showed a typical low-spin type absorptionspectrum with a Soret peak at 419 nm. A partial spectral shiftto the high spin state was observed when trans-cinnamic acidwas added to oxidized P450C4H. By spectral titration, the dissociationconstant of the cinnamic acid-P450C4H complex was determinedto be 2.8 µM. This value is similar to the Km value (1.8µM) for trans-cinnamic acid determined in the reconstitutedsystem. (Received November 20, 1992; Accepted February 17, 1993) 相似文献
10.
Apple seeds soaked in a solution of [±]-[2-14C]abscisicacid for up to 70 d formed phaseate and the epimeric dihydrophaseatesand all four acids were converted into alkali-hydrolysable conjugates.This metabolism occurred in the husks and in the embryos. Bothparts of untreated control seeds contained the four acids andtheir conjugates. In addition to these characterized metabolites,a number of other, labelled, acidic products were isolated fromthe seeds. 14CO2 was evolved from unsterilized seeds but notfrom surface-sterilized ones. Bacterial cultures isolated fromsoil and rotting fruit metabolized [14C]ABA to a range of compounds,but not to phaseic or the dihydro-phaseic acids. A new, acidicconjugate of ABA is described. 相似文献
11.
Leaves of three C4 plants, Setaria italica, Pennisetum typhoides,and Amaranthus paniculatus possessed five- to ten-fold higheractivities of a (Na+-K+)-dependent ATPase than those of twoC3 plants, Oryza sativa and Rumex vesicarius. Na+-K+ ATPasefrom leaves of Amarathus exhibited an optimal pH of 7?5 andan optimal temperature of 35 ?C. It required 40 mM K+ and 80mM Na+ for maximal activity. Ouabain partially inhibited (Na+-K+)-dependentATPase activity in leaves of C4 plants. Ouabain also blockedthe movement of label from initially formed C4 acids into endproducts in leaves of only C4 plants, Setaria and Amaranthusbut not in a C3 plant, Rumex. We propose that Na+-K+ ATPasemay mediate transfer of energy during active transport of C4acids from mesophyll into the bundle sheath. 相似文献
12.
Wheat (Triticum aestivum L.) embryos form in dynamically-regulatedovular environments. Our objectives were to improve developmentof cultured immature wheat embryos by simulating, in vitro,abscisic acid (ABA) levels and O2 tensions as found in wheatovules during zygotic embryogenesis. We characterized from intactwheat kernels embryo respiration, embryo morphology and embryoand endosperm + ABA levels at 13, 19 and 25 d post-anthesis(DPA). Young (13 DPA) embryos were then excised and culturedin vitro, where they were exposed to 0·2 or 2·Ommol m3 ±ABA and 2.·1, 2·5 or 7·4mol m3 (6, 7 and 21%, respectively) gaseous O2. At 6and 12 d in culture, + ABA levels, embryo respiration and embryomorphology were characterized by treatment. Thirteen-day-oldembryos from two different plant populations differed by 17-foldin initial ABA content. However, this difference did not affectprecocious germination in vitro, nor did it affect the amountof exogenous ABA required to reduce precocious germination by40%. In this respect, embryos from both populations were equallysensitive to exogenous ABA. Cavity sap O2 levels (2·1to 2·5 mol m3) were much more effective in preventingprecocious germination of cultured embryos than were cavitysap levels of ABA (0·2 to 2·0 mmol m3).The combination of physiological levels of both ABA and O2 largelynormalized DW accumulation and embryo morphology without alteringendogenous + ABA levels. Residual respiration of cultured embryoswas higher than that of embryos grown in situ, and was not influencedby the exogenous O2 and ABA treatments Key words: Abscisic acid, embryo development, oxygen tensions, respiration, wheat 相似文献
13.
Kreuzwieser Jrgen; Herschbach Cornelia; Stulen Ineke; Wiersema Peter; Vaalburg Willem; Rennenberg Heinz 《Journal of experimental botany》1997,48(7):1431-1438
The processes of NO3 uptake and transport and the effectsof NH4+ or L-glutamate on these processes were investigatedwith excised non-mycorrhizal beech (Fagus sylvatica L.) roots.NO3 net uptake followed uniphasic Michaelis-Menten kineticsin a concentration range of 10µM to 1 mM with an apparentKm of 9.2 µM and a Vmax of 366 nmol g1 FW h1.NH4+, when present in excess to NO3, or 10 mM L-glutamateinhibited the net uptake of NO3 Apparently, part of NO3taken up was loaded into the xylem. Relative xylem loading ofNO3 ranged from 3.21.6 to 6.45.1% of NO3 netuptake. It was not affected by treatment with NH4+ or L-glutamate.16N/13N double labelling experiments showed that NO3efflux from roots increased with increasing influx of NO3and, therefore, declined if influx was reduced by NH4+ or L-glutamateexposure. From these results it is concluded that NO3net uptake by non-mycorrhizal beech roots is reduced by NH4+or L-glutamate at the level of influx and not at the level ofefflux. Key words: Nitrate transport, net uptake, influx, efflux, ammonium, Fagus, Fagaceae 相似文献
14.
Abscisic acid (105 M) was fed via their petioles to leavesdetached from well watered plants of Xanthium strumartum, whilethe intercellular spaces were flushed with air of known CO2content. A closing response to ABA occurred in the presenceor absence of CO2, and the stomata responded to CO2 whetheror not ABA was supplied to the leaves. A factorial experimentrevealed no interaction between CO2 and ABA, and suggested thattheir effect on the rate of closure was purely additive. Theonly evidence of interdependence between the two corn poundswas a delay in the response to ABA in C0 air, which was moremarked in a high light intensity. A hypothesis which is consistentwith the data is that ABA induces stomatal closure by interferingwith the energy supply required for the active transport processeson which guard cell turgor depends. The inhibitory action ofABA takes longer in CO2-free air because, in the absence ofCO2 fixation, energy is available from chioroplasts as wellas mitochondria. 相似文献
15.
A Model for the Interaction of Low Temperature, ABA, IAA, and CO2 in the Control of Stomatal Behaviour 总被引:5,自引:0,他引:5
In the chilling sensitive (C.S.) species Phaseolus vulgarisit was found that at 22 ?C ABA induced stomatal closure butthis effect was dependent on the presence of CO2. In the absenceof CO2 the effect of ABA was completely lost. In contrast toABA, the effect of IAA at 22 ?C was to increase stomatal openingas the IAA concentration increased from 102 to 10 molm3, and this effect was dependent upon the presence ofCO2. However, at 5 ?C the action of ABA was reversed and itwas found to induce stomatal opening when fed via the transpirationstream in excised leaves. Similarly, the CO2 response characteristicswere reversed at low temperatures as removal of CO2 from theatmosphere caused stomatal closure. However, the effect of IAAat 5 ?C in the presence of CO2 and with or without ABA was toincrease stomatal aperture with increasing IAA concentration.Significantly, ABA was found to have no effect upon aperturein the presence of CO2 when IAA was added. The interactive effectsof ABA, IAA, CO2 and low temperature are discussed in relationto a model proposed by the authors. Key words: IAA, ABA, CO2, Stomata 相似文献
16.
Cytoplasmic pH (pHc) in Chara corallina was measured (from [14C]stribution)as a function of external pH (pH0)and temperature. With pH0near 7, pHc at 25?C is 7.80; pHcincreases by 0.005 pH units?C1 temperature decrease, i.e. pHc at 5 ?C is 7.90. WithpH? near 5.5, the increase in pHc with decreasing temperatureis 0.015 units ?C1 between 25 and 15?C, but 0.005 units?C1 between 15 and 5?C. This implies a more precise regulationof pHc with variations in pHo at 5 or 15 ?C compared with 25?C. The observed dp Hc/dT is generally smaller than the 0.017units ?C1 needed to maintain a constant H+/OH1,or a constant fractional ionization of histidine in protein,with variation in temperature. It is closer to that needed tomaintain the fractional ionization of phosphorylated compoundsor of CO2HCO3 The value of dpHc/dT has importantimplications for several regulatory aspects of cell metabolism.These include (all as a function of temperature) the rates ofenzyme reactions, the H+ at the plasmalemma(and hence the energy available for cotransport processes),and the mechanism for pHc regulation by the control of bidirectionalH+ fluxes at the plasmalemma. 相似文献
17.
Prostaglandin E2 activates outwardly rectifying Cl(-) channels via a cAMP-dependent pathway and reduces cell motility in rat osteoclasts 总被引:1,自引:0,他引:1
Okamoto F Kajiya H Fukushima H Jimi E Okabe K 《American journal of physiology. Cell physiology》2004,287(1):C114-C124
We examined changes in electrical and morphological properties of rat osteoclasts in response to prostaglandin (PG)E2. PGE2 (>10 nM) stimulated an outwardly rectifying Cl current in a concentration-dependent manner and caused a long-lasting depolarization of cell membrane. This PGE2-induced Cl current was reversibly inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB), and tamoxifen. The anion permeability sequence of this current was I > Br Cl > gluconate. When outwardly rectifying Cl current was induced by hyposmotic extracellular solution, no further stimulatory effect of PGE2 was seen. Forskolin and dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP) mimicked the effect of PGE2. The PGE2-induced Cl current was inhibited by pretreatment with guanosine 5'-O-2-(thiodiphosphate) (GDPS), Rp-adenosine 3',5'-cyclic monophosphorothioate (Rp-cAMPS), N-(2-[p-bromocinnamylamino]ethyl)-5-isoquinolinesulfonamide dihydrochloride (H-89), and protein kinase A inhibitors. Even in the absence of nonosteoclastic cells, PGE2 (1 µM) reduced cell surface area and suppressed motility of osteoclasts, and these effects were abolished by Rp-cAMPS or H-89. PGE2 is known to exert its effects through four subtypes of PGE receptors (EP1EP4). EP2 and EP4 agonists (ONO-AE1-259 and ONO-AE1-329, respectively), but not EP1 and EP3 agonists (ONO-DI-004 and ONO-AE-248, respectively), mimicked the electrical and morphological actions of PGE2 on osteoclasts. Our results show that PGE2 stimulates rat osteoclast Cl current by activation of a cAMP-dependent pathway through EP2 and, to a lesser degree, EP4 receptors and reduces osteoclast motility. This effect is likely to reduce bone resorption. prostanoid receptor agonists; electrophysiology; motile activity; bone resorption 相似文献
18.
The distribution of exogenously-supplied radioactive labelledindol-3-yl-acetic acid (IAA) and gibberellin A1 (GA1) in geotropicallystimulated roots of Norway spruce (Picea abies (L.) Karst.)has been demonstrated. Seedlings were positioned with theirroot tips in 2.1 x 106 M [14C]IAA or 1.3 x 108m 3H-GA1 for 4 and 20 h, respectively. After geotropic stimulationfor 90 min in the horizontal position the root tips were cutlongitudinally in 50 µm thick sections, using a freeze-microtome.The radioactivity in the 14C-IAA treated roots occurred in higherconcentration in the lower than in the upper halves (ratio 1.25:1). A similar trend was observed in the [3H]GA1-treated rootswhere the ratio lower: upper halves was 2.04: 1. The ratio ofradioactivity in right and left halves of vertical roots wasapproximately the same in roots supplied with [14C]IAA and [3H]GA1(1.09: 1). The supplied radioactive compounds were analysed chromatographicallyafter extraction in methanol of 6 mm apical root segments. Onlya small fraction (78 per cent) of the supplied [14C]IAAwas revealed unchanged in the segments. The major part of thechromatographed, labelled compound has not been identified,but on basis of its RF value it is suggested that it may beindol-3-acetyl-aspartic acid (IAAasp). The chromatographic analysis of the [3H]GA,-treated segmentsshowed that only small fractions of this gibberellin has beenconverted to other compounds. These results have been discussed and correlated with knowledgeof plant growth regulators and their participation in root geotropism. Picea abies, spruce, geotropism, gibberellin A1, indol-3-yl-acetic acid, growth regulators, redistribution in roots 相似文献
19.
Characterisation of Non-Uniform Photosynthesis Induced by Abscisic Acid in Leaves Having Different Mesophyll Anatomies 总被引:29,自引:0,他引:29
Terashima Ichiro; Wong Suan-Chin; Osmond C. Barry; Farquhar Graham D. 《Plant & cell physiology》1988,29(3):385-394
The effects of abscisic acid (ABA) on photosynthesis in leavesof Helianthus annuus L. were compared with those in leaves ofVicia faba L. After the ABA treatment, the response of photosyntheticCO2 assimilation rate, A, to calculated intercellular partialpressure of CO2, Pi, (A(pi) relationship) was markedly depressedin H. annuus. A less marked depression was also observed inV.faba. However, when the abaxial epidermes were removed fromthese leaves, neither the maximum rate nor the CO2 responseof photosynthetic oxygen evolution was affected by the applicationof ABA. Starch-iodine tests revealed that photosynthesis was not uniformover the leaves of H. annuus treated with ABA. The starch contentwas diffferent in each bundle sheath extension compartment (thesmallest subdivision of mesophyll by veins with bundle sheathextensions, having an area of ca. 0.25 mm2 and ca. 50 stomata).In some compartments, no starch was detected. The distributionof open stomata, examined using the silicone rubber impressiontechniques, was similar to the pattern of starch accumulation.In V.faba leaves, which lack bundle sheath extensions, distributionof starch was more homogeneous. These results indicate that the apparent non-stomatal inhibitionof photosynthesis by ABA deduced from the depression of A(pi)relationship is an artifact which can be attributed to the non-uniformdistribution of transpiration and photosynthesis over the leaf.Intercellular gaseous environment in the ABA-treated leavesis discussed in relation to mesophyll anatomy.
1 Present address: Department of Botany, Duke University, Durham,NC 27706, U.S.A. (Received September 30, 1987; Accepted January 13, 1988) 相似文献
20.
The metabolic transformation of glycolate to glycine occurringin photosynthesizing cells of Chromatium was investigated bythe radioisotopic technique and by amino acid analysis. By analyzingthe distribution of radiocarbon upon feeding [1-14C] glycolate,[2-14C] glyoxylate and [1-14C] glycine to bacterial cells, itwas demonstrated that glycolate is converted to glycinc viaglyoxylate, and both glycolate and glycine are excreted extracellularly.Although the formation of serine was barely detected by theabove two techniques in both N2 and O2 atmospheres, it was foundthat 14CO2 is evolved quite markedly from both [1-14C] glycolateand [1-14C] glycine fed to the Chromatium cells. Analyticalresults of transient changes in amino acid compositions underatmospheric changes of N2O2 and by the addition of exogenousglycolate in N2 confirm the notion that glycolate is convertedto glycine. Acidic amino acids (glutamic acid and aspartic acid)appear to take part in glycine formation as amino donors. Theformation of glycine from glycolate in a N2 atmosphere suggeststhat an unknown glycolate dehydrogenation reaction may operatein the overall process.
1 This is paper XXXVII in the series Structure and Functionof Chloroplast Proteins. Paper XXXVI is ref. (5). Theresearch was supported in part by grants from the Ministry ofEducation of Japan (No. 111912), the Toray Science Foundation(Tokyo) and the Naito Science Foundation (Tokyo). (Received July 14, 1976; ) 相似文献