Enzyme inhibition - Factbites

Enzyme inhibition - Factbites
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Topic: Enzyme inhibition

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	07prof.htm
		The most dramatic consequences of enzyme inhibition are found in living organisms, where the inhibition of any particular enzyme involved in a primary metabolic sequence will render the entire sequence inoperative, resulting in either serious damage or death of the organism.
		Uncompetitive inhibition occurs when the inhibitor deactivates the enzyme-substrate complex, usually by attaching itself to both the substrate and enzyme molecules of the complex.
		If a patient were administered two or more drugs simultaneously which react within the body with a common enzyme, cofactor, or active species, this could lead to competitive inhibition of the formation of the respective metabolites and produce serious consequences.
	www.engin.umich.edu /~CRE/07chap/html/07prof.htm

	Agripedia, Interactive Multimedia Instructional Agriculture Resources
		Noncompetitive Inhibition: Inhibitor has no effect on substrate binding and catalytically inactivates the enzyme.
		Uncompetitive Inhibition: Inhibitor binds reversibly to the Enzyme Substrate Complex but not to the free enzyme.
		Competitive Inhibition: Inhibitor binds with free enzyme to prevent substrate binding.
	www.ca.uky.edu /agripedia/classes/pls566/READ01.asp

	Please title this page. (frame8.htm)
		Competitive inhibition occurs when a compound has a similar chemical structure to the enzyme substrate.
		Noncompetitive inhibitors bind to the enzyme-substrate complex and block the catalytic step, i.e.
		There are three basic types of reversible inhibition known.
	www.fst.rdg.ac.uk /online/fs355/frame8.htm

	nov4.html
		This type of inhibition is the simplest to understand: We can have a molecule that looks a lot like the substrate (or the transition state) and will therefore bind to the same active site in the enzyme.
		As with everything in life, we will have different types of inhibition, depending on the type of interaction they have with the enzyme and how they affect the binding of the normal substrate and enzyme catalysis.
		In the first section we will be describing reversible inhibition - That means, there will be an equilibrium between the enzyme and the inhibitor, and there won't be a permanent covalent bond formed.
	tonga.usip.edu /gmoyna/biochem341/lecture25.html

	Three ways to regulate the flow of carbon through a pathway:
		noncompetitive inhibition is not reversible, and chemically alters the enzyme.
		It is important to emphasize that competitive inhibition is reversible, and the enzyme is not altered.
		Enzyme level regulation occurs by activation or inhibition of the catalytic activity of an enzyme.
	www.uta.edu /biology/badon/classnotes/3444/Lecture13.htm

	Active site - Wikipedia, the free encyclopedia
		In noncompetitive inhibition, the inhibitor binds to the enzyme at another site, the allosteric site, and this causes a structural change in the enzyme such that the active site is rendered useless.
		Uncompetitive inhibition, is similar to noncompetitive inhibition except that the inhibitor can only bind the enzyme-substrate complex rather than the free enzyme.
		In competitive inhibition, the active site itself is blocked when a molecule chemically similar to the substrate binds to the active site but cannot be processed by the enzyme.
	en.wikipedia.org /wiki/Active_site

	Factors Affecting Enzymes
		Most enzymatic pathways are also regulated by feedback inhibition, but in these cases the end product of the pathway binds at an allosteric site on the first enzyme of the pathway.
		When the product is in abundance, it binds competitively with its enzyme's active site, and as the product is used up, inhibition is reduced and more product can be produced.
		In noncompetitive inhibition, a molecule binds to an enzyme, but not at the active site.
	ntri.tamuk.edu /cell/allosteric.html

	branchedpathreg
		Cumulative feedback inhibition: In cumulative feedback have only one enz 1, and two allosteric sites, but as each endproduct binds activity of enzyme is reduced by 1/2.
		Isofunctional enzyme inhibition: same as above except that have two enzyme 1's, that catalyze the same reaction, but each sensitive to feedback inhibition by different endproducts.
		Inhibition plus activation: Not all endproducts are negative feedback inhibitors.
	faculty.washington.edu /jclara/410/Outlines/branchedpathreg.htm (193 words)

	Chapter11 Transparencies
		Inhibition of the enzymes at the branchpoints causes intermediate to accumulate, and this intermediate then feeds back to inhibit the enzyme catalyzing the first commited step for the entire pathway.
		Enzyme is feedback inhibited by 9 small molecules, most of which obtain nitrogen from glutamine: carbamoyl-phosphate, glucosamine-6-phosphate, tryptophan, histidine, alanine, serine, glycine, CTP and AMP.
		In nitrogen-limited conditions, GS is present in higher amounts in cells, is deadenylylated, and less sensitive to feedback inhibition.
	www.bmb.psu.edu /courses/micro401/Ch11Nt.htm (2079 words)

	Competitive Inhibition
		If a reversible inhibitor can bind to the enzyme active site in place of the substrate, it is described as a "competitive inhibitor." In pure competitive inhibition, the inhibitor is assumed to bind to the free enzyme but not to the enzyme-substrate (ES) complex.
		The Michaelis-Menten, Lineweaver-Burk, and Hanes-Woolf equations can all be modified to include a term that describes the inhibition by I. Choose one of the cases below to consider each of these in more detail:
		There are several graphical methods for detecting and analyzing competitive inhibition.
	cti.itc.virginia.edu /~cmg/Demo/compInh.html (2079 words)

	Inhibition Summary
		For all types of inhibition, the rate law for a Michaelis-Menten enzyme is
		are affected by inhibition, they are increased or decreased in proportion to the fraction of enzyme molecules that are free of inhibitor.
		Therefore, the fraction of enzyme molecules that are free of I (and behaving normally) is
	www.usm.maine.edu /~rhodes/Goodies/InhibSum/InhibSum.html (2079 words)

	question 1.30
		Noncompetitive inhibiton is more of a catch-all for non-physiological inhibition that does not compete with substrate for substrate binding to enzyme.
		Re: noncompetitive vs. allosteric inhibition: noncompetitive inhibitors bind to a site other than the active site and render the enzyme ineffective.
		Allosteric inhibition generally acts by switching the enzyme between two alternative states, an active form and an inactive form.
	www.columbia.edu /cu/biology/courses/c2005/q98/q980130.html (2079 words)

	Inhibition Summary
		are affected by inhibition, they are increased or decreased in proportion to the fraction of enzyme molecules that are free of inhibitor.
		For all types of inhibition, the rate law for a Michaelis-Menten enzyme is
		Therefore, the fraction of enzyme molecules that are free of I (and behaving normally) is
	www.usm.maine.edu /~rhodes/Goodies/InhibSum/InhibSum.html (2079 words)

	Glossary
		Inhibition of the activity of an enzyme by the accumulation of a substance produced further along a metabolic pathway of which the enzyme is a constituent.
		coli, the activity of glutamine synthetase is regulated by both feedback inhibition and the bicyclic cascade system, which makes it extremely responsive to the cell's nitrogen requirements.
		An enzyme that catalyzes the oxidation of hydrogen peroxide (H2O2) of two molecules of glutathione to form oxidized glutathione and two molecules of H2O.
	www.history.nih.gov /exhibits/stadtman/glossary.htm (2196 words)

	Competitive inhibitor - Enpsychlopedia
		In this mode of inhibition, the activity of the enzyme is completely blocked by the inhibitor and increasing the concentration of substrate does not restore enzyme activity.
		In biochemistry one distinguishes two ways in which a molecule may block the action of an enzymes: competitive and noncompetitive inhibition.
		Characteristic for this mode of inhibition is that increasing the concentration of substrate reduces the effect of the inhibitor, and vice-versa.
	www.grohol.com /wiki/Competitive_inhibition (2196 words)

	Inhibition Summary
		are affected by inhibition, they are increased or decreased in proportion to the fraction of enzyme molecules that are free of inhibitor.
		For all types of inhibition, the rate law for a Michaelis-Menten enzyme is
		Therefore, the fraction of enzyme molecules that are free of I (and behaving normally) is
	www.usm.maine.edu /~rhodes/Goodies/InhibSum/InhibSum.html (2196 words)

	Catechol Oxidase (Tyrosinase) - Enzymes
		Competitive inhibition takes place when a molecule that is structurally similar to the substrate for a particular reaction competes for a position at the active site on the enzyme.
		The noncompetitive inhibitor binds to the enzyme at a location away from the active site, either blocking access to the active site or changing the conformation of the enzyme, rendering it inactive.
		Competitive inhibition can be reversed if the concentration of substrate is raised to sufficiently high levels while the concentration of the inhibitor is held constant (Figure3).
	www.science-projects.com /Tyrosinase.htm (2196 words)

	Bioc 462a Lecture Notes
		Enzyme inhibition (and many other biochemical phenomena, including effect of binding of one ligand to a protein on the binding of another ligand to that protein) can be understood in the context of a "linked function" diagram, a thermodynamic box.
		xample 1: irreversible inhibition of enzymes that have
		Penicillin irreversibly (covalently) inhibits an enzyme involved in bacterial cell wall synthesis.
	www.biochem.arizona.edu /classes/bioc462/462a/NOTES/ENZYMES/enzyme_kinetics3.html (2196 words)

	NonCompetitive Inhibition
		However, when the non-competitive inhibitor binds to the enzyme at the regulatory site, the shape of the active site changes so that it can no longer bind its substrate or catalyze the production of product.
		The enzyme will remain inhibited until the non-competitive inhibitor leaves the regulatory site.
		Click on the animation to see a larger view.
	bio.winona.msus.edu /berg/ANIMTNS/n-c-inan.htm (2196 words)

	Dictionary.com/INHIBITION
		The condition in which or the process by which an enzyme, for example, is inhibited.
		The condition in which or the process by which an enzyme is inhibited.
		Any of a variety of processes that are associated with the gradual attenuation, masking, and extinction of a previously conditioned response.
	dictionary.reference.com /search?q=INHIBITION (2196 words)

	Pharmacy Update, November/December 2001
		Inhibition of this isoenzyme is likely to reduce the analgesic effect of codeine and codeine-derivatives (42).
		For noncompetitive inhibition substrate binds to one site on the enzyme while the inhibitor binds to another site, thereby making the enzyme-substrate-inhibitor complex nonfunctional.
		For example, inhibition of terfenadine metabolism may result in QT prolongation and torsades de pointes while inhibition of sertraline metabolism is not associated with such serious cardiovascular sequelae.
	www.cc.nih.gov /phar/updates/novdec01/page5-novdec01.html (2196 words)

	Inhibitors
		Irreversible inhibition usually results from a covalent and permanent modification of a functional group on the enzyme, rendering the molecule inactive.
		Mixed inhibition may be considered a consequence of several kinds of inhibition.
		Inhibition may be of two kinds, reversible and irreversible.
	www.bio.davidson.edu /Biology/jowilliamson/Techniques/Protocolweek8.html (2196 words)

	Enzymes
		In feedback inhibition, the allosteric effect lowers the affinity of the enzyme for its substrate.
		In the case if feedback inhibition and precursor activation, the activity of the enzyme is being regulated by a molecule which is not its substrate.
		The inhibition is called competitive because if you increase the ratio of succinic to malonic acid in the mixture, you will gradually restore the rate of catalysis.
	users.rcn.com /jkimball.ma.ultranet/BiologyPages/E/Enzymes.html (1853 words)

	Simple Inhibitors of Enzymes and their Kinetic Analysis
		The noncompetitive inhibitor, Inc, forms a complex with enzyme, which is unaffected by the substrate concentration, such that it does not matter if substrate is already bound to the enzyme when the noncompetitive inhibitor binds or not.
		A noncompetitive inhibitor is a substance with no chemical similarity to substrate and its inhibition can not be overcome by high concentration of substrate.
		In this classical type of noncompetitive inhibition, the Km is not altered and only the Vmax is decreased.
	www.bio.mtu.edu /campbell/bl4820/lectures/lec3/482ek4.htm (1853 words)

	CHE 415 - General Biochemistry I - Lecture 11, Basic Enzymatic Reaction Kinetics
		Noncompetitive inhibition involves a separate binding site on the enzyme for the inhibitor, such that substrate still has access to the active site, but cannot form the catalytically competent enzyme/ substrate complex.
		malonate inhibition of succinate dehydrogenase, which uses succinate as the substrate.
		example of competitive inhibition is that of phosphoglycerate mutase by the product of its reaction, 2,3-bisphosphoglycerate, with the substrate, 1,3-bisphosphoglycerate.
	people.uis.edu /efish1/Che415/Lectur11/lectur11.htm (1853 words)

	Abstract 57
		So, the observed mixed inhibition kinetics by substrate analogs is curious.
		The mode of inhibition by each analog is reversible and mixed with respect to the substrate, methylmalonyl-CoA.
		This implies that the inhibitors are able to bind to both free enzyme and to the enzyme-substrate complex, although with affinities that are 4.5- to 10-fold different for the two species.
	uts.cc.utexas.edu /~liulab/abstracts/58.htm (1853 words)

	BioAct
		Glyphosate inhibits the action of the enzyme 5-enolpyruvoylshikimate-3-phosphate synthetase (EPSPS) which is involved in the biosynthesis of essential aromatic compounds, such as the aromatic amino-acids
		Glyphosate displays a unique affinity for EPSPS and does not interfere with the action of any other enzyme which uses PEP as a substrate which means that glyphosate cannot behave simply as a ground state mimic for PEP.
		It has been hypothesised that the only glyphosate-based herbicidal compounds which act via EPSPS inhibition are those which breakdown, for what ever reason, to form the glyphosate anion.
	www.ch.ic.ac.uk /local/projects/j_england/BioAct.html (400 words)

	16,17-dihydro gibberellin A5 competitively inhibits a recombinant Arabidopsis GA 3beta-hydroxylase encoded by the GA4 gene.
		For the exo-isomer of dihydro GA5, inhibition increased with the dose of dihydro GA5, with Lineweaver-Burk plots showing that dihydro GA5 changed only the Km of the enzyme reaction, not the V(max), giving a dissociation constant of the enzyme-inhibitor complex (Ki) of 70 microM.
		16,17-dihydro gibberellin A5 competitively inhibits a recombinant Arabidopsis GA 3beta-hydroxylase encoded by the GA4 gene.This behavior is consistent with dihydro GA5, at least, functioning as a competitive substrate inhibitor of AtGA3ox1.
		Ring D-modified gibberellin (GA) A5 and A20 derivatives are structurally similar to GA20 and GA9 (the precursors to growth-active GA1 and GA4) and, when applied to higher plants, especially grasses, can reduce shoot growth with concomitant reductions in levels of growth-active GAs and increases in levels of their immediate 3-deoxy precursors.
	www.pdg.cnb.uam.es /UniPub/iHOP/gp/10451999.html (288 words)

	401lec17p4.html
		This is of course related to non-competitive inhibition of the enzyme, but we discussed only the case where the enzyme loses activity but can still bind its substrate normally, which we called a classic non-competitive inhibitor.
		The biosynthesis of amino acids is often regulated by Feedback Inhibition (in those organisms that make amino acids since not all do).
		Model of Feedback Inhibition using a metabolic pathway to illustrate this concept.
	www.bio.mtu.edu /campbell/401lec17p4.html (462 words)

	Ch431_Lec_15Oct
		Note that in each case we can predict/explain the pattern of inhibition on the basis of the substrate and inhibitor binding to the same "enzyme form." Thus for the Ordered Sequential mechanism only the first substrate and last product bind to the same form, in this case the free enzyme.
		Competitive Inhibition: S and I are mutually exclusive, E can bind to one OR the other.
		We can model this inhibition with chemical equations, keeping in mind that S and I are mutually exclusive, E can bind to one OR the other:
	www.humboldt.edu /~rap1/C431.F01/C431Notes/C431n15oct.htm (462 words)

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