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https://hdl.handle.net/1822/7977
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Campo DC | Valor | Idioma |
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dc.contributor.author | Guimarães, Pedro M. R. | - |
dc.contributor.author | Multanen, Jyri-Pekka | - |
dc.contributor.author | Domingues, Lucília | - |
dc.contributor.author | Teixeira, J. A. | - |
dc.contributor.author | Londesborough, John | - |
dc.date.accessioned | 2008-07-16T19:43:07Z | - |
dc.date.available | 2008-07-16T19:43:07Z | - |
dc.date.issued | 2008-05 | - |
dc.identifier.citation | "Applied and Environmental Microbiology". ISSN 0099-2240. 74:10 (May 2008) 3076-3084. | eng |
dc.identifier.issn | 0099-2240 | eng |
dc.identifier.uri | https://hdl.handle.net/1822/7977 | - |
dc.description.abstract | Initial rates of sugar uptake (zero-trans rates) are often measured by incubating yeast cells with radiolabeled sugars for 5 to 30 s and determining the radioactivity entering the cells. The yeast cells used are usually harvested from growth medium, washed, suspended in nutrient-free buffer, and stored on ice before they are assayed. With this method, the specific rates of zero-trans lactose uptake by Kluyveromyces lactis or recombinant Saccharomyces cerevisiae strains harvested from lactose fermentations were three- to eightfold lower than the specific rates of lactose consumption during fermentation. No significant extracellular β-galactosidase activity was detected. The ATP content and adenylate energy charge (EC) of the yeasts were relatively low before the [14C]lactose uptake reactions were started. A short (1- to 7-min) preincubation of the yeasts with 10 to 30 mM glucose caused 1.5- to 5-fold increases in the specific rates of lactose uptake. These increases correlated with increases in EC (from 0.6 to 0.9) and ATP (from 4 to 8 µmol·g dry yeast–1). Stimulation by glucose affected the transport Vmax values, with smaller increases in Km values. Similar observations were made for maltose transport, using a brewer's yeast. These findings suggest that the electrochemical proton potential that drives transport through sugar/H+ symports is significantly lower in the starved yeast suspensions used for zero-trans assays than in actively metabolizing cells. Zero-trans assays with such starved yeast preparations can produce results that seriously underestimate the capacity of sugar/H+ symports. A short exposure to glucose allows a closer approach to the sugar/H+ symport capacity of actively metabolizing cells. | eng |
dc.description.sponsorship | Fundação para a Ciência e a Tecnologia (FCT) | por |
dc.description.sponsorship | Finnish Malting and Brewing industry (PBL) | por |
dc.language.iso | eng | eng |
dc.publisher | American Society for Microbiology (ASM) | eng |
dc.rights | openAccess | eng |
dc.title | Stimulation of zero-trans rates of lactose and maltose uptake into yeasts by preincubation with hexose to increase the adenylate energy charge | eng |
dc.type | article | por |
dc.peerreviewed | yes | eng |
sdum.number | 10 | eng |
sdum.pagination | 3076–3084 | eng |
sdum.publicationstatus | published | eng |
sdum.volume | 74 | eng |
oaire.citationStartPage | 3076 | por |
oaire.citationEndPage | 3084 | por |
oaire.citationIssue | 10 | por |
oaire.citationVolume | 74 | por |
dc.identifier.doi | 10.1128/AEM.00188-08 | por |
dc.identifier.pmid | 18378647 | por |
dc.subject.wos | Science & Technology | por |
sdum.journal | Applied and Environmental Microbiology | por |
Aparece nas coleções: | CEB - Publicações em Revistas/Séries Internacionais / Publications in International Journals/Series |
Ficheiros deste registo:
Ficheiro | Descrição | Tamanho | Formato | |
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Guimaraes2_AEM[2].pdf | 760,1 kB | Adobe PDF | Ver/Abrir |