1
|
Del Río E, Acién FG, García-Malea MC, Rivas J, Molina-Grima E, Guerrero MG. Efficiency assessment of the one-step production of astaxanthin by the microalga Haematococcus pluvialis. Biotechnol Bioeng 2008; 100:397-402. [PMID: 18098317 DOI: 10.1002/bit.21770] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Continuous cultivation of Haematococcus pluvialis under moderate nitrogen limitation represents a straightforward strategy, alternative to the classical two-stage approach, for astaxanthin production by this microalga. Performance of the one-step system has now been validated for more than 40 combinations of dilution rate, nitrate concentration in the feed medium, and incident irradiance, steady state conditions being achieved and maintained in all instances. Specific nitrate input and average irradiance were decisive parameters in determining astaxanthin content of the biomass, as well as productivity of the system. The growth rate of the continuous photoautotrophic cultures was a hyperbolic function of average irradiance. As long as specific nitrate input was above the threshold value of 2.7 mmol/g day, cells performed green and astaxanthin was present at basal levels only. Below the threshold value, under moderate nitrogen limitation conditions, astaxanthin accumulated to reach cellular levels of up to 1.1% of the dry biomass. Increasing irradiance resulted in enhancement of astaxanthin accumulation when nitrogen input was limiting, but never under nitrogen sufficiency. Mean daily productivity values of 20.8 +/- 2.8 mg astaxanthin/L day (1.9 +/- 0.3 g dry biomass/L day) were consistently achieved for a specific nitrate input of about 0.8 mmol/g day and an average irradiance range of 77-110 microE/m(2) s. Models relating growth rate and astaxanthin accumulation with both average irradiance and specific nitrate input fitted accurately experimental data. Simulations provided support to the contention of achieving efficient production of the carotenoid through convenient adjustment of the determining parameters, and yielded productivity estimates for the one-step system higher than 60 mg astaxanthin/L day. The demonstrated capabilities of this production system, as well as its product quality, made it a real alternative to the current two-stage system for the production of astaxanthin-rich biomass.
Collapse
Affiliation(s)
- Esperanza Del Río
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-Consejo Superior de Investigaciones Científicas, Centro de Investigaciones Científicas Isla de la Cartuja, Avda. Américo Vespucio, 49, 41092-Sevilla, Spain
| | | | | | | | | | | |
Collapse
|
2
|
Radisavljevic Z, George M, Dries DJ, Gamelli RL. Determination of Intracellular and Extracellular Nitrite and Nitrate by Anion Chromatography. J LIQ CHROMATOGR R T 2006. [DOI: 10.1080/10826079608006302] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Zivotije Radisavljevic
- a Burn-Shock Trauma , Institute Loyola University-Chicago School of Medicine , Building 110/4th 2160 South First Avenue, Maywood , IL , 60153
| | - Magdalena George
- a Burn-Shock Trauma , Institute Loyola University-Chicago School of Medicine , Building 110/4th 2160 South First Avenue, Maywood , IL , 60153
| | - David J. Dries
- a Burn-Shock Trauma , Institute Loyola University-Chicago School of Medicine , Building 110/4th 2160 South First Avenue, Maywood , IL , 60153
| | - Richard L. Gamelli
- a Burn-Shock Trauma , Institute Loyola University-Chicago School of Medicine , Building 110/4th 2160 South First Avenue, Maywood , IL , 60153
| |
Collapse
|
3
|
Del Río E, Acién FG, García-Malea MC, Rivas J, Molina-Grima E, Guerrero MG. Efficient one-step production of astaxanthin by the microalgaHaematococcus pluvialis in continuous culture. Biotechnol Bioeng 2005; 91:808-15. [PMID: 15937954 DOI: 10.1002/bit.20547] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The performance of Haematococcus pluvialis in continuous photoautotrophic culture has been analyzed, especially from the viewpoint of astaxanthin production. To this end, chemostat cultures of Haematococcus pluvialis were carried out at constant light irradiance, 1,220 microE/m2.s, and dilution rate, 0.9/d, but varying the nitrate concentration in the feed medium reaching the reactor, from 1.7 to 20.7 mM. Both growth and biomass composition were affected by the nitrate supply. With saturating nitrate, the biomass productivity was high, 1.2 g/L.d, but astaxanthin accumulation did not take place, the C/N ratio of the biomass being 5.7. Under moderate nitrate limitation, biomass productivity was decreased, as also did biomass concentration at steady state, whereas accumulation of astaxanthin developed and the C/N ratio of the biomass increased markedly. Astaxanthin accumulation took place in cells growing and dividing actively, and its extent was enhanced in response to the limitation in nitrate availability, with a recorded maximum for astaxanthin cellular level of 0.8% of dry biomass and of 5.6 mg/L.d for astaxanthin productivity. The viability of a significant continued generation of astaxanthin-rich H. pluvialis cells becomes thus demonstrated, as also does the continuous culture option as an alternative to current procedures for the production of astaxanthin using this microalga. The intensive variable controlling the behavior of the system has been identified as the specific nitrate input, and a mathematical model developed that links growth rate with both irradiance and specific nitrate input. Moreover, a second model for astaxanthin accumulation, also as a function of irradiance and specific nitrate input, was derived. The latter model takes into account that accumulation of astaxanthin is only partially linked to growth, being besides inhibited by excess nitrate. Simulations performed fit experimental data and emphasize the contention that astaxanthin can be efficiently produced under continuous mode by adjustment of the specific nitrate input, predicting even higher values for astaxanthin productivity. The developed models represent a powerful tool for management of such an astaxanthin-generating continuous process, and could allow the development of improved systems for the production of astaxanthin-rich Haematococcus cells.
Collapse
Affiliation(s)
- Esperanza Del Río
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-Consejo Superior de Investigaciones Científicas, Avda. Américo Vespucio, 49, 41092-Sevilla, Spain
| | | | | | | | | | | |
Collapse
|
4
|
Miyado T, Nagai H, Takeda S, Saito K, Fukushi K, Yoshida Y, Wakida SI, Niki E. Development of a novel running buffer for the simultaneous determination of nitrate and nitrite in human serum by capillary zone electrophoresis. J Chromatogr A 2003; 1014:197-202. [PMID: 14558625 DOI: 10.1016/s0021-9673(03)00944-0] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In order to improve NO2- peak height and obtain a convenient buffer system for the assay of nitrogen monooxide metabolites, we developed a novel running buffer for the simultaneous determination of nitrite and nitrate in human serum by capillary electrophoresis. The addition of cetyltrimethylammonium chloride to the running buffer resulted in high-speed separation using reverse electroosmotic flow. Highly sensitive determination was also achieved using stacking with 10-fold diluted sample solutions. The samples were injected hydrodynamically for 100 s into a 50 cm x 75 microm I.D. capillary. The separation voltage was 10 kV (negative polarity). UV detection was performed at 214 nm. We obtained complete separation of nitrite and nitrate in deproteinized human serum within 6 min with optimum analytical conditions. Linear calibration curves for nitrite and nitrate for both peak height and peak area were obtained with standard addition method. The limits of detection obtained at a signal-to-noise ratio of 3 for nitrite and nitrate were 4.1 and 2.0 microM, while the values of relative standard deviation of peak height were 2.4 and 2.6%, respectively.
Collapse
Affiliation(s)
- Takashi Miyado
- Human Stress Signal Research Center, National Institute of Advanced Industrial Science and Technology, AIST Kansai, 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577, Japan
| | | | | | | | | | | | | | | |
Collapse
|
5
|
Abstract
Nitrate assimilation has received much attention in filamentous fungi and plants but not so much in yeasts. Recently the availability of classical genetic and molecular biology tools for the yeast Hansenula polymorpha has allowed the advance of the study of this metabolic pathway in yeasts. The genes YNT1, YNR1 and YNI1, encoding respectively nitrate transport, nitrate reductase and nitrite reductase, have been cloned, as well as two other genes encoding transcriptional regulatory factors. All these genes lie closely together in a cluster. Transcriptional regulation is the main regulatory mechanism that controls the levels of the enzymes involved in nitrate metabolism although other mechanisms may also be operative. The process involved in the sensing and signalling of the presence of nitrate in the medium is not well understood. In this article the current state of the studies of nitrate assimilation in yeasts as well as possible venues for future research are reviewed.
Collapse
Affiliation(s)
- José M Siverio
- Departamento de Bioquímica y Biología Molecular, Grupo del Metabolismo del Nitrógeno, Universidad de La Laguna, E-38206 La Laguna, Tenerife, Spain.
| |
Collapse
|
6
|
Wood NJ, Alizadeh T, Richardson DJ, Ferguson SJ, Moir JWB. Two domains of a dual-function NarK protein are required for nitrate uptake, the first step of denitrification in Paracoccus pantotrophus. Mol Microbiol 2002; 44:157-70. [PMID: 11967076 DOI: 10.1046/j.1365-2958.2002.02859.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Uptake of nitrate into the cytoplasm is the first but least well understood step of denitrification; no gene has previously been identified to be necessary for this process. Upstream from the structural genes of the membrane-bound nitrate reductase (narGHJI) in Paracoccus pantotrophus there is a fusion of two genes, each homologous to members of the narK family. The single open reading frame is predicted to encode 24 transmembrane helices, comprising two domains, NarK1 and NarK2. Analysis of both the accumulation of intracellular nitrite and electron transport through the nitrate reductase enzyme in narK mutants reveals that NarK1 and NarK2 are both involved in nitrate uptake. Maximal rate of nitrate transport via NarK2 was dependent upon nitrite, indicating that NarK2 encodes a nitrate/nitrite antiporter. The uncouplers S13 and dinitrophenol showed that NarK2 was not dependent on the proton motive force for maximal nitrate transport activity. Nitrate transport via NarK1 was dependent on proton motive force, indicating that it is likely to be a nitrate/proton symporter. Low expression of membrane-bound nitrate reductase in narK mutants was counteracted by azide, which induced nitrate reductase expression only if the transcriptional activator NarR was present.
Collapse
Affiliation(s)
- Nicholas J Wood
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK
| | | | | | | | | |
Collapse
|
7
|
Kouretas PC, Kim YD, Cahill PA, Myers AK, To LN, Wang YN, Sitzmann JV, Hannan RL. Nonanticoagulant heparin prevents coronary endothelial dysfunction after brief ischemia-reperfusion injury in the dog. Circulation 1999; 99:1062-8. [PMID: 10051301 DOI: 10.1161/01.cir.99.8.1062] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Coronary endothelial dysfunction after brief ischemia-reperfusion (IR) remains a clinical problem. We investigated the role of heparin and N-acetylheparin, a nonanticoagulant heparin derivative, in modulating coronary endothelial function after IR injury, with an emphasis on defining the role of the nitric oxide (NO)-cGMP pathway in the heparin-mediated effect. METHODS AND RESULTS Male mongrel dogs were surgically instrumented, and the effects of both bovine heparin and N-acetylheparin on coronary endothelial vasomotor function, expressed as percent change from baseline flow after acetylcholine challenge, were studied after 15 minutes of regional ischemia of the left anterior descending artery (LAD) followed by 120 minutes of reperfusion. In dogs treated with placebo (saline), coronary vasomotor function was significantly (P</=0.03) decreased after 15 and 30 minutes of reperfusion (65+/-12% and 73+/-12%) compared with preischemia (103+/-6%). In contrast, the vasodilatory response to the endothelium-independent vasodilator sodium nitroprusside was maintained during reperfusion. Preischemic administration of both bovine heparin and N-acetylheparin (6.0 mg/kg IV) preserved coronary endothelial function throughout reperfusion. In a parallel group of dogs, nitrate/nitrite (NOx) and cGMP levels in the LAD were measured after treatment and during 15-minute reperfusion. Preischemic administration of N-acetylheparin caused a significant increase in basal NOx and cGMP levels compared with saline controls. Pretreatment with N-acetylheparin also caused a significant increase in NOx and cGMP levels in the LAD after 15 minutes of reperfusion compared with IR alone. CONCLUSIONS These results suggest that heparin preserves coronary endothelial function after brief IR injury by a mechanism independent of its anticoagulant activity and that the effect of heparin may be mediated in part by activation of the NO-cGMP pathway.
Collapse
Affiliation(s)
- P C Kouretas
- Departments of Surgery, Physiology and Biophysics, Georgetown University Medical Center, Washington, DC, USA
| | | | | | | | | | | | | | | |
Collapse
|
8
|
Rodríguez R, Kobayashi M, Omata T, Lara C. Independence of carbon and nitrogen control in the posttranslational regulation of nitrate transport in the cyanobacterium Synechococcus sp. strain PCC 7942. FEBS Lett 1998; 432:207-12. [PMID: 9720926 DOI: 10.1016/s0014-5793(98)00865-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Nitrate transport by Synechococcus sp. strain PCC 7942 cells was inhibited by ammonium and by inhibitors of CO2 fixation. Ammonium assimilation inhibitors, such as L-methionine D,L-sulfoximine, were known to prevent the negative effects of ammonium and of inhibitors of CO2 fixation on nitrate uptake, leading to propose that CO2 fixation was required to counteract the feed-back inhibition of nitrate assimilation. In NR-less mutants, L-methionine D,L-sulfoximine prevented the negative effects of ammonium on nitrate transport, but not always prevented those of inhibiting CO2 fixation. The carboxy-terminal domain of the NrtC subunit of the nitrate transporter has recently been identified as a regulatory domain involved in N-control. The mutant strain NC2, constructed by deleting the 3' portion of nrtC, showed high nitrate transport activity insensitive to ammonium but sensitive to inhibitors of CO2 fixation. These findings indicate that the C-control and the N-control of nitrate transport are independent at both the physiological and the molecular level.
Collapse
Affiliation(s)
- R Rodríguez
- Dept. de Bioquímica Vegetal y Biología Molecular, Facultad de Biología, Universidad de Sevilla, Spain
| | | | | | | |
Collapse
|
9
|
Lee HM, Flores E, Herrero A, Houmard J, Tandeau de Marsac N. A role for the signal transduction protein PII in the control of nitrate/nitrite uptake in a cyanobacterium. FEBS Lett 1998; 427:291-5. [PMID: 9607331 DOI: 10.1016/s0014-5793(98)00451-7] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
In the cyanobacterium Synechococcus sp. strain PCC 7942, ammonium exerts a rapid and reversible inhibition of the nitrate and nitrite uptake, and the PII protein (GlnB) is differentially phosphorylated depending on the intracellular N/C balance. RNA/DNA hybridizations, as well as nitrate and nitrite uptake experiments, were carried out with the wild-type strain and a PII-null mutant. The transcriptional control by ammonium of the expression of the nir-nrt ABCD-narB operon remained operative in the mutant but, in contrast to the wild-type strain, the mutant took up nitrate and nitrite even in the presence of ammonium. Moreover, the wild-type phenotype was restored by insertion of a copy of the wild-type glnB gene in the genome of the PII-null mutant. These results indicate that the unphosphorylated form of PII is involved in the short-term inhibition by ammonium of the nitrate and nitrite uptake in Synechococcus sp. strain PCC 7942.
Collapse
Affiliation(s)
- H M Lee
- Département de Biochimie et Génétique Moléculaire, Unité de Physiologie Microbienne, Paris, France
| | | | | | | | | |
Collapse
|
10
|
Friedberg MA, Hinsdale ME, Shihabi ZK. Analysis of nitrate in biological fluids by capillary electrophoresis. J Chromatogr A 1997; 781:491-6. [PMID: 9368397 DOI: 10.1016/s0021-9673(97)00583-9] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Nitrite and nitrate represent the products of the final pathway of nitric oxide metabolism. These two ions were analyzed by capillary electrophoresis (CE) in serum, cerebrospinal fluid, urine and tissue homogenates by mixing the sample with acetonitrile containing NaBr as an internal standard, followed by centrifugation. The supernatant was injected hydrodynamically on a capillary 50 cm x 75 microns (I.D.) and electrophoresed at 6 kV (reversed polarity) in 1.4% sodium chloride in phosphate buffer for 13 min with detection at 214 nm. In addition to removal of the proteins, acetonitrile caused sample stacking. Urinary nitrate analysis by CE was compared to that by the enzymatic Aspergillus nitrate reductase method, with a correlation coefficient of 0.96.
Collapse
Affiliation(s)
- M A Friedberg
- Department of Pathology, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, NC 27157, USA
| | | | | |
Collapse
|
11
|
Kucera I, Kaplan P, Zeman A. Oxygen increases the steady-state level of nitrate in denitrifying cells of Paracoccus denitrificans. FEMS Microbiol Lett 1996; 145:163-6. [PMID: 8961552 DOI: 10.1111/j.1574-6968.1996.tb08572.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The levels of nitrate in denitrifying cells of Paracoccus denitrificans were determined by centrifugation through silicone oil into phosphoric acid and ion-exchange HPLC analysis of the cell lysates, using [14C]sucrose to correct for the trapped external medium. Introduction of oxygen brought about a significant upward shift in the intracellular nitrate concentration. This result calls into question the current thinking that oxygen blocks nitrate respiration primarily due to the inhibition of nitrate transport into the cell.
Collapse
Affiliation(s)
- I Kucera
- Department of Biochemistry, Faculty of Science, Masaryk University, Brno, Czech Republic.
| | | | | |
Collapse
|
12
|
Muscará MN, de Nucci G. Simultaneous determination of nitrite and nitrate anions in plasma, urine and cell culture supernatants by high-performance liquid chromatography with post-column reactions. JOURNAL OF CHROMATOGRAPHY. B, BIOMEDICAL APPLICATIONS 1996; 686:157-64. [PMID: 8971596 DOI: 10.1016/s0378-4347(96)00229-0] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A high-performance liquid chromatographic method for the determination of nitrite and nitrate anions derived from nitric oxide in biological fluids is presented. After separation on a strong anion-exchange column (Spherisorb SAX, 250 x 4.6 mm I.D., 5 microns), two on-line post-column reactions occur. The first involves nitrate reduction to nitrite on a copper-plated cadmium-filled column. In the second, the diazotization-coupling reaction between nitrite and the Griess reagent (0.05% naphtylethylendiamine dihydrochloride plus 0.5% sulphanilamide in 5% phosphoric acid) takes place, and the absorbance of the chromophore is read at 540 nm. This methodology was applied to biological fluids. Before injection into the chromatographic system, the samples were diluted and submitted to suitable clean-up procedures (urine and cell culture supernatant samples are passed through C18 cartridges, and serum samples were deproteinized by ultrafiltration through membranes with a molecular mass cut-off of 3000). The method has a sensitivity of 30 pmol for both anions, as little as 0.05-0.1 ml sample volume is required and linearity is observed up to 60 nmol for each anion.
Collapse
Affiliation(s)
- M N Muscará
- Miguel Servet Clinical Pharmacology Unit, Department of Pharmacology, Faculty of Medical Sciences, UNICAMP, Campinas, SP, Brazil
| | | |
Collapse
|
13
|
Kučera I, Kaplan P. A study on the transport and dissimilatory reduction of nitrate in Paracoccus denitrificans using viologen dyes as electron donors. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1996. [DOI: 10.1016/0005-2728(96)00079-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
|
14
|
Muñoz-centeno MC, Paneque A, Cejudo FJ. Cyanate is transported by the nitrate permease in Azotobacter chroococcum. FEMS Microbiol Lett 1996. [DOI: 10.1111/j.1574-6968.1996.tb08088.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
|
15
|
Rodríguez R, Guerrero MG, Lara C. Mechanism of sodium/nitrate symport in Anacystis nidulans R2. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1994. [DOI: 10.1016/0005-2728(94)90121-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
16
|
Dobao MM, Mart�nez-Luque M, Castillo F. Nitrate reductase activity in spheroplasts from Rhodobacter capsulatus E1F1 requires a periplasmic protein. Arch Microbiol 1993. [DOI: 10.1007/bf00245308] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
17
|
Quesada A, Galván A, Schnell RA, Lefebvre PA, Fernández E. Five nitrate assimilation-related loci are clustered in Chlamydomonas reinhardtii. MOLECULAR & GENERAL GENETICS : MGG 1993; 240:387-94. [PMID: 8413188 DOI: 10.1007/bf00280390] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Three overlapping clones covering a Chlamydomonas reinhardtii genomic region of about 32 kb appear to contain five genes potentially involved in nitrate assimilation in addition to the nitrate reductase structural locus nit-1. These new loci produced transcripts of 2.8, 2.2, 1.8 and 1.7 kb in nitrate-induced wild-type cells that, like the 3.4 kb transcript of nit-1, were undetectable in cells grown in ammonium. In addition, in a mutant defective at the regulatory locus, nit-2 for nitrate assimilation, which does not express the nit-1 gene transcript, accumulation of the four other transcripts was also blocked. They have been named nar (nitrate assimilation related) genes. The nar-1 and nar-2 loci are transcribed in the same orientation as nit-1. The nar-3 and nar-4 loci are transcribed divergently from nit-1. DNA and RNA sequences from both nar-3 and nar-4 cross-hybridized with each other indicating that they share similar sequences. Four nitrate assimilation-deficient mutants (C2, D2, F6 and G1) were characterized. These mutants lack nar transcripts and have major deletions and/or rearrangements in the nar gene cluster. In contrast to other nitrate reductase-deficient mutants and to wild type, deletion mutants and the regulatory mutant nit-2 were incapable of accumulating intracellular nitrate. Two of the mutants in which expression of all the nar loci did not occur, C2 and D2, grew in nitrite medium and showed wild-type levels of both nitrite uptake and nitrite reductase activities.(ABSTRACT TRUNCATED AT 250 WORDS)
Collapse
Affiliation(s)
- A Quesada
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias, Universidad de Córdoba, Spain
| | | | | | | | | |
Collapse
|
18
|
Maguire GA, Horsfield JA. Investigation of the use of impermeable fluid barriers between pelleted and supernatant enzyme activity in a pseudohomogeneous enzyme immunoassay. Ann Clin Biochem 1992; 29 ( Pt 5):546-50. [PMID: 1444167 DOI: 10.1177/000456329202900510] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
We have investigated the feasibility of performing an automated pseudohomogeneous enzyme immunoassay in which a separation step is not apparent to the user. This was achieved using a layer of silicone fluid, which is immiscible with aqueous solutions, as a physical barrier between the pelleted and supernatant enzyme. Initially we produced a manual assay based on the Serozyme T4 assay to demonstrate the feasibility of the approach. This assay showed good precision, parallelism and correlated with 'in house' results on patients' samples. Production of a fully automated assay was made difficult by the design of available equipment but none the less we demonstrated the feasibility of the automated approach by producing a standard curve for T4.
Collapse
Affiliation(s)
- G A Maguire
- Department of Clinical Biochemistry, Addenbrookes Hospital, Cambridge, UK
| | | |
Collapse
|
19
|
Rodríguez R, Lara C, Guerrero MG. Nitrate transport in the cyanobacterium Anacystis nidulans R2. Kinetic and energetic aspects. Biochem J 1992; 282 ( Pt 3):639-43. [PMID: 1554347 PMCID: PMC1130835 DOI: 10.1042/bj2820639] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Nitrate transport has been studied in the cyanobacterium Anacystis nidulans R2 by monitoring intracellular nitrate accumulation in intact cells of the mutant strain FM6, which lacks nitrate reductase activity and is therefore unable to reduce the transported nitrate. Kinetic analysis of nitrate transport as a function of external nitrate concentration revealed apparent substrate inhibition, with a peak velocity at 20-25 microM-nitrate. A Ks (NO3-) of 1 microM was calculated. Nitrate transport exhibited a stringent requirement for Na+. Neither Li+ nor K+ could substitute for Na+. Monensin depressed nitrate transport in a concentration-dependent manner, inhibition being more than 60% at 2 microM, indicating that the Na(+)-dependence of active nitrate transport relies on the maintenance of a Na+ electrochemical gradient. The operation of an Na+/NO3- symport system is suggested. Nitrite behaved as an effective competitive inhibitor of nitrate transport, with a Ki (NO2-) of 3 microM. The time course of nitrite inhibition of nitrate transport was consistent with competitive inhibition by mixed alternative substrates. Nitrate and nitrite might be transported by the same carrier.
Collapse
Affiliation(s)
- R Rodríguez
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, Spain
| | | | | |
Collapse
|
20
|
Galván A, Cárdenas J, Fernández E. Nitrate Reductase Regulates Expression of Nitrite Uptake and Nitrite Reductase Activities in Chlamydomonas reinhardtii. PLANT PHYSIOLOGY 1992; 98:422-6. [PMID: 16668656 PMCID: PMC1080205 DOI: 10.1104/pp.98.2.422] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
In Chlamydomonas reinhardtii mutants defective at the structural locus for nitrate reductase (nit-1) or at loci for biosynthesis of the molybdopterin cofactor (nit-3, nit-4, or nit-5 and nit-6), both nitrite uptake and nitrite reductase activities were repressed in ammonium-grown cells and expressed at high amounts in nitrogen-free media or in media containing nitrate or nitrite. In contrast, wild-type cells required nitrate induction for expression of high levels of both activities. In mutants defective at the regulatory locus for nitrate reductase (nit-2), very low levels of nitrite uptake and nitrite reductase activities were expressed even in the presence of nitrate or nitrite. Both restoration of nitrate reductase activity in mutants defective at nit-1, nit-3, and nit-4 by isolating diploid strains among them and transformation of a structural mutant upon integration of the wild-type nit-1 gene gave rise to the wild-type expression pattern for nitrite uptake and nitrite reductase activities. Conversely, inactivation of nitrate reductase by tungstate treatment in nitrate, nitrite, or nitrogen-free media made wild-type cells respond like nitrate reductase-deficient mutants with respect to the expression of nitrite uptake and nitrite reductase activities. Our results indicate that nit-2 is a regulatory locus for both the nitrite uptake system and nitrite reductase, and that the nitrate reductase enzyme plays an important role in the regulation of the expression of both enzyme activities.
Collapse
Affiliation(s)
- A Galván
- Departamento de Bioquímica y Biología Molecular y Fisiología, Facultad de Ciencias, Universidad de Córdoba, E-14071 Córdoba, Spain
| | | | | |
Collapse
|
21
|
MartÃnez-Luque M, Dobao M, Castillo F. Characterization of the assimilatory and dissimilatory nitrate-reducing systems inRhodobacter: a comparative study. FEMS Microbiol Lett 1991. [DOI: 10.1111/j.1574-6968.1991.tb04485.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
|