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dc.contributor.author | Fontes, Rui | - |
dc.contributor.author | Meireles Ribeiro, João | - |
dc.contributor.author | Sillero, Antonio | - |
dc.date.accessioned | 2010-05-11T12:32:41Z | - |
dc.date.available | 2010-05-11T12:32:41Z | - |
dc.date.issued | 2000 | - |
dc.identifier.citation | Acta Biochimica Polonica 47(1): 233-257 (2000) | en_US |
dc.identifier.issn | 0001-527X | - |
dc.identifier.uri | http://hdl.handle.net/10261/24187 | - |
dc.description | 25 pages, 9 figures, 6 tables, 21 equations, 2 appendix. | en_US |
dc.description.abstract | A combined analysis of enzyme inhibition and activation is presented, based on a rapid equilibrium model assumption in which one molecule of enzyme binds one molecule of substrate (S) and/or one molecule of a modifier X. The modifier acts as activator (essential or non-essential), as inhibitor (total or partial), or has no effect on the reaction rate (v), depending on the values of the equilibrium constants, the rate constants of the limiting velocity steps, and the concentration of substrate ([S]). Different possibilities have been analyzed from an equation written to emphasize that v = f([X]) is, in general and at a fixed [S], a hyperbolic function. Formulas for Su (the value of [S], different from zero, at which v is unaffected by the modifier) and v(su) (v at that particular [S]) were deduced. In Lineweaver-Burk plots, the straight lines related to different [X] generally cross in a point (P) with coordinates (Su, v(su)). In certain cases, point P is located in the first quadrant which implies that X acts as activator, as inhibitor, or has no effect, depending on [S]. Furthermore, we discuss: (1) the apparent Vmax and Km displayed by the enzyme in different situations; (2) the degree of effect (inhibition or activation) observed at different concentrations of substrate and modifier; (3) the concept of Ke, a parameter that depends on the concentration of substrate and helps to evaluate the effect of the modifier: it equals the value of [X] at which the increase or decrease in the reaction rate is half of that achieved at saturating [X]. Equations were deduced for the general case and for particular situations, and used to obtain computer-drawn graphs that are presented and discussed. Formulas for apparent Vmax, Km and Ke have been written in a way making it evident that these parameters can be expressed as pondered means. | en_US |
dc.description.sponsorship | Supported by grants from Dirección General de Investigación Científica y Técnica (PM95/0013 and PM98/0129, A.S.; PM97/0022, J.M.R.) and from Comunidad de Madrid (08.9/0004/98, to A.S.). R.F. was supported by a fellowship from Junta Nacional de Investigação Científica e Tecnológica (Portugal). During part of this work, J.M.R. held a postdoctoral fellowship from Consejería de Educación y Juventud, Junta de Extremadura (Spain; PRI9606B064), cofinanced by the Fondo Social Europeo. | en_US |
dc.format.extent | 363687 bytes | - |
dc.format.mimetype | application/pdf | - |
dc.language.iso | eng | en_US |
dc.publisher | Polish Scientific Publishers | en_US |
dc.rights | openAccess | en_US |
dc.subject | Enzyme activation | en_US |
dc.subject | Enzyme inhibition | en_US |
dc.subject | Enzyme kinetics | en_US |
dc.subject | Enzyme modifier | en_US |
dc.subject | Graphical presentations | en_US |
dc.subject | I50 | en_US |
dc.subject | Rapid equilibrium kinetics | en_US |
dc.title | Inhibition and activation of enzymes. The effect of a modifier on the reaction rate and on kinetic parameters | en_US |
dc.type | artículo | en_US |
dc.description.peerreviewed | Peer reviewed | en_US |
dc.relation.publisherversion | http://www.actabp.pl/#File?./html/1_2000/233.html | en_US |
dc.type.coar | http://purl.org/coar/resource_type/c_6501 | es_ES |
item.fulltext | With Fulltext | - |
item.languageiso639-1 | en | - |
item.openairecristype | http://purl.org/coar/resource_type/c_18cf | - |
item.openairetype | artículo | - |
item.cerifentitytype | Publications | - |
item.grantfulltext | open | - |
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Inhibition and activation of enzymes.pdf | 355,16 kB | Adobe PDF | Visualizar/Abrir |
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