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Yuan Y, DeBrosse M, Brothers M, Kim S, Sereda A, Ivanov NV, Hussain S, Heikenfeld J. Oil-Membrane Protection of Electrochemical Sensors for Fouling- and pH-Insensitive Detection of Lipophilic Analytes. ACS APPLIED MATERIALS & INTERFACES 2021; 13:53553-53563. [PMID: 34665962 DOI: 10.1021/acsami.1c14175] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
To take full advantage of the reagent- and label-free sensing capabilities of electrochemical sensors, a frequent and remaining challenge is interference and degradation of the sensors due to uncontrolled pH or salinity in the sample solution or foulants from the sample solution. Here, we present an oil-membrane sensor protection technique that allows for the permeation of hydrophobic (lipophilic) analytes into a sealed sensor compartment containing ideal salinity and pH conditions while simultaneously blocking common hydrophilic interferents (proteins, acids, bases, etc.) In this paper, we validate the oil-membrane sensor protection technique by demonstrating continuous cortisol detection via electrochemical aptamer-based (EAB) sensors. The encapsulated EAB cortisol sensor exhibits a 5 min concentration-on rise time and maintains a measurement signal of at least 7 h even in the extreme condition of an acidic solution of pH 3.
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Affiliation(s)
- Yuchan Yuan
- Novel Devices Lab, University of Cincinnati, Cincinnati, Ohio 45221, United States
| | - Madeleine DeBrosse
- Novel Devices Lab, University of Cincinnati, Cincinnati, Ohio 45221, United States
- 711 Human Performance Wing, Air Force Research Laboratory, Wright-Patterson AFB, Ohio 45433, United States
| | - Michael Brothers
- 711 Human Performance Wing, Air Force Research Laboratory, Wright-Patterson AFB, Ohio 45433, United States
| | - Steve Kim
- 711 Human Performance Wing, Air Force Research Laboratory, Wright-Patterson AFB, Ohio 45433, United States
| | | | | | - Saber Hussain
- 711 Human Performance Wing, Air Force Research Laboratory, Wright-Patterson AFB, Ohio 45433, United States
| | - Jason Heikenfeld
- Novel Devices Lab, University of Cincinnati, Cincinnati, Ohio 45221, United States
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Whole Cell Biotransformation of 1-dodecanol by Escherichia coli by Soluble Expression of ADH Enzyme from Yarrowia lipolytica. BIOTECHNOL BIOPROC E 2021. [DOI: 10.1007/s12257-020-0176-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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3
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Callejas-Negrete OA, Torres-Guzmán JC, Padilla-Guerrero IE, Esquivel-Naranjo U, Padilla-Ballesteros MF, García-Tapia A, Schrank A, Salazar-Solís E, Gutiérrez-Corona F, González-Hernández GA. The Adh1 gene of the fungus Metarhizium anisopliae is expressed during insect colonization and required for full virulence. Microbiol Res 2015; 172:57-67. [DOI: 10.1016/j.micres.2014.11.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Revised: 11/18/2014] [Accepted: 11/25/2014] [Indexed: 12/22/2022]
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Muzaffar M, Ahmad A. The mechanism of enhanced insulin amyloid fibril formation by NaCl is better explained by a conformational change model. PLoS One 2011; 6:e27906. [PMID: 22132167 PMCID: PMC3221682 DOI: 10.1371/journal.pone.0027906] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2011] [Accepted: 10/27/2011] [Indexed: 01/05/2023] Open
Abstract
The high propensity of insulin to fibrillate causes severe biomedical and biotechnological complications. Insulin fibrillation studies attain significant importance considering the prevalence of diabetes and the requirement of functional insulin in each dose. Although studied since the early years of the 20(th) century, elucidation of the mechanism of insulin fibrillation has not been understood completely. We have previously, through several studies, shown that insulin hexamer dissociates into monomer that undergoes partial unfolding before converting into mature fibrils. In this study we have established that NaCl enhances insulin fibrillation mainly due to subtle structural changes and is not a mere salt effect. We have carried out studies both in the presence and absence of urea and Gdn.HCl and compared the relationship between conformation of insulin induced by urea and Gdn.HCl with respect to NaCl at both pH 7.4 (hexamer) and pH 2 (monomer). Fibril formation was followed with a Thioflavin T assay and structural changes were monitored by circular dichroism and size-exclusion chromatography. The results show salt-insulin interactions are difficult to classify as commonly accepted Debye-Hückel or Hofmeister series interactions but instead a strong correlation between the association states and conformational states of insulin and their propensity to fibrillate is evident.
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Affiliation(s)
- Mahvish Muzaffar
- Department of Biological Chemistry and Life Sciences Institute, University of Michigan, Ann Arbor, Michigan, United States of America
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5
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Pritsch K, Courty PE, Churin JL, Cloutier-Hurteau B, Ali MA, Damon C, Duchemin M, Egli S, Ernst J, Fraissinet-Tachet L, Kuhar F, Legname E, Marmeisse R, Müller A, Nikolova P, Peter M, Plassard C, Richard F, Schloter M, Selosse MA, Franc A, Garbaye J. Optimized assay and storage conditions for enzyme activity profiling of ectomycorrhizae. MYCORRHIZA 2011; 21:589-600. [PMID: 21344212 DOI: 10.1007/s00572-011-0364-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2010] [Accepted: 01/28/2011] [Indexed: 05/30/2023]
Abstract
The aim of a joint effort by different research teams was to provide an improved procedure for enzyme activity profiling of field-sampled ectomycorrhizae, including recommendations on the best conditions and maximum duration for storage of ectomycorrhizal samples. A more simplified and efficient protocol compared to formerly published procedures was achieved by using manufactured 96-filter plates in combination with a vacuum manifold and by optimizing incubation times. Major improvements were achieved by performing the series of eight enzyme assays with a single series of root samples instead of two series, reducing the time needed for sample preparation, minimizing error-prone steps such as pipetting and morphotyping, and facilitating subsequent DNA analyses due to the reduced sequencing effort. The best preservation of samples proved to be storage in soil at 4-6 °C in the form of undisturbed soil cores containing roots. Enzyme activities were maintained for up to 4 weeks under these conditions. Short-term storage of washed roots and ectomycorrhizal tips overnight in water did not cause substantial changes in enzyme activity profiles. No optimal means for longer-term storage by freezing at -20 °C or storage in 100% ethanol were recommended.
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Affiliation(s)
- Karin Pritsch
- Institute of Soil Ecology, German Research Center for Environmental Health (GmbH), 85764, Neuherberg, Germany.
| | - Pierre Emanuel Courty
- UMR 1136, Interactions Arbres Micro-organismes, Centre INRA de Nancy, 54280, Champenoux, France
- Botanical Institute, University of Basel, 4056, Basel, Switzerland
| | - Jean-Louis Churin
- UMR 1136, Interactions Arbres Micro-organismes, Centre INRA de Nancy, 54280, Champenoux, France
| | - Benoit Cloutier-Hurteau
- UMR 1222, Ecologie Fonctionelle et Biogéochimie des Sols, INRA/IRD/SupAgro, 34060, Montpellier Cedex 01, France
| | - Muhammad Arif Ali
- UMR 1222, Ecologie Fonctionelle et Biogéochimie des Sols, INRA/IRD/SupAgro, 34060, Montpellier Cedex 01, France
| | - Coralie Damon
- UMR CNRS 5557 d'Ecologie Microbienne, Université de Lyon, Université Lyon 1, 69622, Villeurbanne Cedex, France
| | - Myriam Duchemin
- UMR 1222, Ecologie Fonctionelle et Biogéochimie des Sols, INRA/IRD/SupAgro, 34060, Montpellier Cedex 01, France
| | - Simon Egli
- Swiss Federal Research Institute WSL, 8903, Birmensdorf, Switzerland
| | - Jana Ernst
- Institute of Soil Ecology, Terrestrial Ecogenetics, German Research Center for Environmental Health (GmbH), 85764, Neuherberg, Germany
| | - Laurence Fraissinet-Tachet
- UMR CNRS 5557 d'Ecologie Microbienne, Université de Lyon, Université Lyon 1, 69622, Villeurbanne Cedex, France
| | - Francisco Kuhar
- Biodiversidad y Biología Experimental, CABA, Universidad de Buenos Aires, Buenos Aires, 1428, Argentina
- Institute of Soil Ecology, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), 85764, Neuherberg, Germany
| | - Elvira Legname
- UMR 1222, Ecologie Fonctionelle et Biogéochimie des Sols, INRA/IRD/SupAgro, 34060, Montpellier Cedex 01, France
| | - Roland Marmeisse
- UMR CNRS 5557 d'Ecologie Microbienne, Université de Lyon, Université Lyon 1, 69622, Villeurbanne Cedex, France
| | - Alex Müller
- Swiss Federal Research Institute WSL, 8903, Birmensdorf, Switzerland
| | - Petia Nikolova
- Institute of Soil Ecology, German Research Center for Environmental Health (GmbH), 85764, Neuherberg, Germany
| | - Martina Peter
- Swiss Federal Research Institute WSL, 8903, Birmensdorf, Switzerland
| | - Claude Plassard
- UMR 1222, Ecologie Fonctionelle et Biogéochimie des Sols, INRA/IRD/SupAgro, 34060, Montpellier Cedex 01, France
| | - Franck Richard
- UMR 5175, Centre d'Ecologie Fonctionnelle et Evolutive, 34293, Montpellier 5, France
| | - Michael Schloter
- Institute of Soil Ecology, Terrestrial Ecogenetics, German Research Center for Environmental Health (GmbH), 85764, Neuherberg, Germany
| | - Marc-André Selosse
- UMR 5175, Centre d'Ecologie Fonctionnelle et Evolutive, 34293, Montpellier 5, France
| | - Alain Franc
- UMR Biodivers Genes & Communautes, INRA Pierroton, 33612, Cestas, France
| | - Jean Garbaye
- UMR 1136, Interactions Arbres Micro-organismes, Centre INRA de Nancy, 54280, Champenoux, France
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de Smidt O, du Preez JC, Albertyn J. The alcohol dehydrogenases ofSaccharomyces cerevisiae: a comprehensive review. FEMS Yeast Res 2008; 8:967-78. [DOI: 10.1111/j.1567-1364.2008.00387.x] [Citation(s) in RCA: 164] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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7
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Markossian KA, Golub NV, Khanova HA, Levitsky DI, Poliansky NB, Muranov KO, Kurganov BI. Mechanism of thermal aggregation of yeast alcohol dehydrogenase I. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2008; 1784:1286-93. [DOI: 10.1016/j.bbapap.2008.04.030] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2008] [Revised: 04/14/2008] [Accepted: 04/24/2008] [Indexed: 11/17/2022]
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8
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Khodagholi F, Yazdanparast R. Cooperative effects of artificial chaperone and Mg2+ ions on alkaline phosphatase refolding. Biochem Eng J 2007. [DOI: 10.1016/j.bej.2007.02.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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9
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Guo KK, Ren J. Cardiac overexpression of alcohol dehydrogenase (ADH) alleviates aging-associated cardiomyocyte contractile dysfunction: role of intracellular Ca2+ cycling proteins. Aging Cell 2006; 5:259-65. [PMID: 16842498 DOI: 10.1111/j.1474-9726.2006.00215.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Aging is a complex biological process with contributions from a wide variety of genes including insulin-like growth factor I and alcohol dehydrogenase (ADH), which decline with advanced age. The goal of this study was to examine if ADH enzyme plays any role in cardiac aging. Ventricular myocytes were isolated from young (2-3 months old) or aged (26-28 months old) male FVB wild-type and cardiac-specific ADH (class I, isozyme type 1) transgenic mice. Mechanical properties were measured using an IonOptix system. Aged FVB myocytes displayed significantly reduced ADH activity compared with young ones, which was restored by the ADH transgene. Compared with young cardiomyocytes, aged FVB myocytes exhibited prolonged relengthening duration and a steaper decline in peak shortening amplitude in response to elevated electrical stimuli. Although ADH transgene itself did not alter mechanical properties in young mice, it rescued aging-associated diastolic dysfunction without affecting dampened contractile response to high stimulus frequency. Immunoblot analysis revealed reduced sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA2a) and Na(+)-Ca(2+) exchanger (NCX) levels in conjunction with enhanced phospholamban expression in aged FVB hearts. ADH transgene prevented aging-induced reduction in SERCA2a and NCX without affecting up-regulated phospholamban. Our data suggest that aging is associated with a reduced ADH enzymatic activity and diastolic dysfunction, which may be corrected with cardiac overexpression of the ADH enzyme. Alteration in cardiac Ca(2+) cycling proteins including SERCA2a and NCX may play a role in both pathogenesis of cardiac aging and the beneficial effect of ADH enzyme.
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Affiliation(s)
- Kelly K Guo
- Division of Pharmaceutical Sciences & Center for Cardiovascular Research and Alternative Medicine, University of Wyoming, Laramie, WY 82071, USA
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Zhang YX, Zhu Y, Xi HW, Liu YL, Zhou HM. Refolding and reactivation of calf intestinal alkaline phosphatase with excess magnesium ions. Int J Biochem Cell Biol 2002; 34:1241-7. [PMID: 12127574 DOI: 10.1016/s1357-2725(02)00055-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
It is well known that Mg(2+) is an essential component in many biological processes. This research investigated the courses of both the reactivation and the refolding in the absence and presence of Mg(2+) ions. Calf intestinal alkaline phosphatase (CIP) was extensively denatured in 3 M guanidine hydrochloride (GdnHCl) solution for 2 h. Under suitable renaturation conditions, about 60-70% of the activity was recovered in the absence and presence of different magnesium ion concentrations. The refolding processes followed two-phase courses, whereas the reactivation processes were monophasic after dilution in proper solutions with or without Mg(2+). The magnesium ions affected both the reactivation and the refolding courses of unfolded CIP. A comparison of rate constants for the refolding of unfolded CIP with those for recovery of enzyme activity at different Mg(2+) concentrations showed that they were not synchronized. The activity recovery was speeded up due to the presence of Mg(2+) ions; while the refolding course of unfolded CIP was somewhat inhibited by the excess Mg(2+).
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Affiliation(s)
- Ying-Xia Zhang
- Department of Chemistry, Capital University of Medical Science, Beijing 100054, PR China
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11
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Park TJ, Paik WK, Lim IK. Induction of thermal and chemical stability of O6-methylguanine-DNA methyltransferase by Ca2+. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1599:36-44. [PMID: 12479403 DOI: 10.1016/s1570-9639(02)00379-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Divalent cations stabilized rat recombinant O6-methylguanine-DNA methyltransferase (rMGMT) protein against heat treatment. Activity of rMGMT was completely abolished by incubating at 45 degrees C for 30 min, however, addition of 1.0 mM Mg2+, Ca2+ or Mn2+ significantly protected heat-induced inactivation of MGMT activity (50-60% vs. 97% inactivation). Protective effect of Ca2+ on the MGMT activity was concentration-dependent up to 3 mM, and the thermal protection was effective up to 45 degrees C. In order to investigate Ca2+ binding site in rMGMT protein, truncated GST-rMGMT proteins containing N-terminal 39 amino acids (GST-rMGMT39), 70 amino acids (GST-rMGMT70) and full-length protein (GST-rMGMT) were prepared. Radiolabeled calcium ion [45Ca2+] was bound only to the GST-rMGMT70 and GST-rMGMT, but not to the GST-rMGMT39, indicating that divalent cations could bind the residues between 40th and 70th of the rMGMT protein. Calcium binding was not observed in the site-directed mutant rMGMT proteins (rMGMT(D42A) and rMGMT(E45A)), confirmed by autoradiography using [45Ca2+] after nondenaturing gel electrophoresis; however, the above two mutants had the same catalytic activity as well as proteolytic sensitivity as the wild MGMT protein. Analysis by equilibrium dialysis revealed stoichiometric binding of one molecule of Ca2+ to one molecule of the protein. Since circular dichroism (CD) spectra indicated no discernible difference before and after Ca2+ binding, the above results suggested that neutralization of two negative charges of Asp42 and Glu45 by Ca2+ resulted in thermal stabilization of the protein with minimum perturbation of its tertiary structure.
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Affiliation(s)
- Tae Jun Park
- Department of Biochemistry and Molecular Biology, Ajou University School of Medicine, Suwon 442-721, Gyunggi-do, South Korea
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12
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Ahmad A, Akhtar MS, Bhakuni V. Monovalent cation-induced conformational change in glucose oxidase leading to stabilization of the enzyme. Biochemistry 2001; 40:1945-55. [PMID: 11329261 DOI: 10.1021/bi001933a] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Glucose oxidase (GOD) from Aspergillus niger is an acidic dimeric enzyme having a high degree of localization of negative charges on the enzyme surface and dimer interface. We have studied the effect of monovalent cations on the structure and stability of GOD using various optical spectroscopic techniques, limited proteolysis, size exclusion chromatography, differential scanning calorimetry, and enzymic activity measurements. The monovalent cations were found to influence the enzymic activity and tertiary structure of GOD, but no effect on the secondary structure of the enzyme was observed. The monovalent cation-stabilized GOD was found to have a more compact dimeric structure but lower enzymic activity than the native enzyme. The enzyme's K(m) for D-glucose was found to be slightly enhanced for the monovalent cation-stabilized enzyme (maximum enhancement of about 35% for LiCl) as compared to native GOD. Comparative denaturation studies on the native and monovalent cation-stabilized enzyme demonstrated a significant resistance of cation-stabilized GOD to urea (about 50% residual activity at 6.5 M urea) and thermal denaturation (Delta T(m) maximum of 10 degrees C compared to native enzyme). However, pH-induced denaturation showed a destabilization of monovalent cation-stabilized GOD as compared to the native enzyme. The effectiveness of monovalent cations in stabilizing GOD structure against urea and thermal denaturation was found to follow the Hofmeister series: K(+) > Na(+) > Li(+).
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Affiliation(s)
- A Ahmad
- Division of Membrane Biology, Central Drug Research Institute, Lucknow 226 001, India
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Zhao Y, Wang G, Cao Z, Wang Y, Cheng H, Zhou HM. Effects of Ca2+ on the activity and stability of methanol dehydrogenase. JOURNAL OF PROTEIN CHEMISTRY 2000; 19:469-73. [PMID: 11195971 DOI: 10.1023/a:1026597314542] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The effects of exogenously added Ca2+ on the enzymatic activity and structural stability of methanol dehydrogenase were studied for various Ca2+ concentrations. Methanol dehydrogenase activity increased significantly with increasing concentration of Ca2+, approaching saturation at 200 mM Ca2+. The effect of Ca2+ on the activation of MDH was time dependent and Ca2+ specific and was due to binding of the metal ions to the enzyme. Addition of increasing concentration of Ca2+ caused a decrease of the intrinsic tryptophan fluorescence intensity in a concentration-dependent manner to a minimum at 200 mM, but with no change in the fluorescence emission maximum wavelength or the CD spectra. The results revealed that the activation of methanol dehydrogenase by Ca2+ occurred concurrently with the conformational change. In addition, exogenously bound Ca2+ destabilized MDH. The potential biological significance of these results is discussed.
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Affiliation(s)
- Y Zhao
- Department of Biochemistry and Biophysics, College of Life Scineces, Wuhan University, China
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Vanni A, Pessione E, Anfossi L, Baggiani C, Cavaletto M, Gulmini M, Giunta C. Properties of a cobalt-reactivated form of yeast alcohol dehydrogenase. ACTA ACUST UNITED AC 2000. [DOI: 10.1016/s1381-1177(99)00108-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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15
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Mahler G, Nudel C. Effect of magnesium ions on fermentative and respirative functions in Pichia stipitis under oxygen-restricted growth. Microbiol Res 2000; 155:31-5. [PMID: 10830897 DOI: 10.1016/s0944-5013(00)80019-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Mg2+ level affected growth, xylitol and ethanol production by P. stipitis grown under microaerophilic conditions. Low Mg2+ level (1 mM) directed the C flux from ethanol to xylitol, with no effect on xylose consumption rate. The addition of pyrazole, an alcohol dehydrogenase (ADH) inhibitor, had the same effect, even in conditions of Mg2+ excess (4 mM), indicating a negative interaction between ADH and Mg2+ ions (p << 0.01). Cells grown either with pyrazole or Mg limitation increased their intracellular NADH concentration about 3 times, but displayed no significant differences in ADH specific activities (1,000 U/mg protein, +/- 10%). In contrast, no interaction was measured between Mg and antimycin A, excluding the possibility that Mg2+ limitation interferes with respiration.
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Affiliation(s)
- G Mahler
- Department of Industrial Microbiology and Biotechnology, Faculty of Pharmacy and Biochemistry, University of Buenos Aires, Argentina
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Park YD, Zhou HM. Effect of Mg2+ during reactivation and refolding of guanidine hydrochloride-denatured creatine kinase. JOURNAL OF PROTEIN CHEMISTRY 2000; 19:193-8. [PMID: 10981811 DOI: 10.1023/a:1007003703087] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Creatine kinase (ATP: creatine N-phosphotransferase, EC 2.7.3.2) was completely denatured using 3 M guanidine hydrochloride for 2 h as in previous studies [Yao et al. (1982), Sci. Sin. 25B, 1296-1302; Yao et al. (1984), Biochemistry 23, 2740-2744; Yao et al. (1982), Sci. Sin. 25B, 1186-1193]. Under suitable conditions, about 60-70% of the activity can be recovered in the presence of different Mg2+ concentrations. Both the reactivation and the refolding processes follow two-phase courses after dilution in the proper solutions. A comparison of the rate constants for the refolding of unfolded creatine kinase with those for the recovery of its catalytic activity at various Mg2+ concentrations shows that these are not synchronized. The reactivity of guanidine hydrochloride-denatured creatine kinase can be inhibited by Mg2+; however, the rates of reactivation are independent of the Mg2+ concentration. In addition, Mg2+ affects the fluorescence intensity, but the rate constants of refolding are independent of Mg2+ concentration. Although the reactivation of GdHCl-denatured creatine kinase is complete about 3 h after dilution with reactivation solutions, the conformational changes during refolding occur in a much slower reaction. Mg2+ can induce complex changes in the relative fluorescence intensity during refolding over a broad range of concentrations.
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Affiliation(s)
- Y D Park
- Department of Biological Science and Biotechnology, Tsinghua University, Beijing, China
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17
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Madern D, Zaccai G. Stabilisation of halophilic malate dehydrogenase from Haloarcula marismortui by divalent cations -- effects of temperature, water isotope, cofactor and pH. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 249:607-11. [PMID: 9370373 DOI: 10.1111/j.1432-1033.1997.00607.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Halophilic malate dehydrogenase is stable in a limited concentration range of MgCl2 or CaCl2. Thermal deactivation of the protein at low concentrations of these divalent salts is very different from that occurring at high concentrations. In low salt, stability always increases as the temperature is lowered. In high salt, stability shows bell-shaped behaviour as a function of temperature: increasing to a maximum at 4 degrees C, and subsequently decreasing as the temperature is lowered. This is in contrast to other salts, for which the deactivation behaviour depends on the salt type but not on its concentration. Cofactor addition or replacement of H2O by D2O modify only the deactivation at low MgCl2 or CaCl2 concentrations. A pH transition between pH 7 and pH 8, however, modified enzyme deactivation at both low and high MgCl2 or CaCl2 concentrations. The pH effect on stability was also observed in other salts. By comparing the effect of CaCl2, MgCl2, and NaCl, a strong correlation was found between the minimum salt concentration required for the stabilisation of halophilic malate dehydrogenase and the hydration of the cation.
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Affiliation(s)
- D Madern
- Institut de Biologie Structurale, CEA-CNRS, Grenoble, France
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