Ebook Enzymes - Biochemistry, biotechnology and clinical chemistry (2/E): Part 2
➤ Gửi thông báo lỗi ⚠️ Báo cáo tài liệu vi phạmNội dung chi tiết: Ebook Enzymes - Biochemistry, biotechnology and clinical chemistry (2/E): Part 2
Ebook Enzymes - Biochemistry, biotechnology and clinical chemistry (2/E): Part 2
12The Binding of Ligands to Proteins12.1INTRODUCTIONIn this chapter, we will discuss the binding of ligands to monomeric and oligomeric proteins. Anyt Ebook Enzymes - Biochemistry, biotechnology and clinical chemistry (2/E): Part 2thing which binds to an enzyme or other protein is a ligand, regardless of whether or not it is a substrate and undergoes a subsequent reaction. Here, in general, we will be considering binding processes where no subsequent reaction is taking place, e.g. the binding to a protein of a non-substrate, Ebook Enzymes - Biochemistry, biotechnology and clinical chemistry (2/E): Part 2or of a substrate for a two-substrate reaction in the absence of the second substrate. However, we will briefly consider what effects the binding charEbook Enzymes - Biochemistry, biotechnology and clinical chemistry (2/E): Part 2
acteristics might have on the kinetics of any subsequent reaction. We will also take into consideration the possibility of interaction between binding12The Binding of Ligands to Proteins12.1INTRODUCTIONIn this chapter, we will discuss the binding of ligands to monomeric and oligomeric proteins. Anyt Ebook Enzymes - Biochemistry, biotechnology and clinical chemistry (2/E): Part 2l sub-unit).12.2THE BINDING OF A LIGAND TO A PROTEIN HAVING A SINGLE LIGAND-BINDING SITEConsider the binding of a ligand (S) to a protein (E), in the simplest possible system: E + s ES.The binding constant Kb is defined by the relationship:Kb = [ES]/([E][S]) (note that Kb = 1//Q-12.1The fractional s Ebook Enzymes - Biochemistry, biotechnology and clinical chemistry (2/E): Part 2aturation (Ỵ) of the protein is given by:Y = [ES] _ [ESI _ Xb[E][S] _ Kb[S] [Eo] [E] + [ES] [E]+Ab[E][S] l+Kb[S]-12.2From this, it can be seen that aEbook Enzymes - Biochemistry, biotechnology and clinical chemistry (2/E): Part 2
plot of Y against [S] at constant [E(>] will be hyperbolic (Fig. 12.1).Sec. 12.3]Fig. 12.1 - Graph of fractional saturation (K) against ligand concent12The Binding of Ligands to Proteins12.1INTRODUCTIONIn this chapter, we will discuss the binding of ligands to monomeric and oligomeric proteins. Anyt Ebook Enzymes - Biochemistry, biotechnology and clinical chemistry (2/E): Part 2s the first step in a process whereby a product p is formed. If the reaction proceeds under steady-stale conditions, where [So] » [Eo] and [S] ~ [So], then [ES] does not vary with time and, in the most straightforward system, Vo is proportional to [ES]. Under these conditions,= FES1 :■' [Eq]v0K ' ma Ebook Enzymes - Biochemistry, biotechnology and clinical chemistry (2/E): Part 2x-123so a graph of Vo against [So] will be the same shape as that of Y against [S], i.e. hyperbolic. This hyperbolic relationship between Vo and [So]Ebook Enzymes - Biochemistry, biotechnology and clinical chemistry (2/E): Part 2
under steady-state conditions is, of course, predicted by the Michaelis-Mcnlcn equation (see sections 7.1.1 and 7.1.2).If, on the other hand, the reac12The Binding of Ligands to Proteins12.1INTRODUCTIONIn this chapter, we will discuss the binding of ligands to monomeric and oligomeric proteins. Anyt Ebook Enzymes - Biochemistry, biotechnology and clinical chemistry (2/E): Part 2haracteristics of the reaction will not usually run parallel to the binding characteristics.12.3COOPERATIVITYIf more than one ligand-binding site is present on a protein, there is a possibility of interaction between the binding sites during the binding process. This is termed cooperativity.Positive Ebook Enzymes - Biochemistry, biotechnology and clinical chemistry (2/E): Part 2 cooperativity is said to occur when the binding of one molecule of a substrate of ligand increases the affinity of the protein for other molecules ofEbook Enzymes - Biochemistry, biotechnology and clinical chemistry (2/E): Part 2
the same or different substrate or ligandNegative cooperativity occurs when the binding of one molecule of a substrate of ligand decreases the affini12The Binding of Ligands to Proteins12.1INTRODUCTIONIn this chapter, we will discuss the binding of ligands to monomeric and oligomeric proteins. Anyt Ebook Enzymes - Biochemistry, biotechnology and clinical chemistry (2/E): Part 2 a substrate or ligand affects the binding to the protein of subsequent molecules of the same substrate or ligand (i.e. the binding of one molecule of A affects the binding of further molecules of A).224The Binding of Ligands to Proteins[Ch. 12Heterotropic cooperativity occurs when the binding of on Ebook Enzymes - Biochemistry, biotechnology and clinical chemistry (2/E): Part 2e molecule of a substrate or ligand affects the binding to the protein of molecules of a different substrate or ligand (i.e. the binding of one molecuEbook Enzymes - Biochemistry, biotechnology and clinical chemistry (2/E): Part 2
le of A affects the binding of B).Cooperative effects may be positive and homotropic, positive and hcterotropic, negative and homotropic, or negative 12The Binding of Ligands to Proteins12.1INTRODUCTIONIn this chapter, we will discuss the binding of ligands to monomeric and oligomeric proteins. Anyt Ebook Enzymes - Biochemistry, biotechnology and clinical chemistry (2/E): Part 2ositive hctcrotropic cooperativity.12.4POSITIVE HOMOTROPIC COOPERATIVITY AND THE HILL EQUATIONLet us consider the simplest case of positive homotropic cooperativity in a dimeric protein. There arc two identical ligand-binding sites, and when the ligand binds to one, it increases the affinity of the Ebook Enzymes - Biochemistry, biotechnology and clinical chemistry (2/E): Part 2protein for the ligand at the other site, so the reaction sequence is:M2 + s gtow > M,s12The Binding of Ligands to Proteins12.1INTRODUCTIONIn this chapter, we will discuss the binding of ligands to monomeric and oligomeric proteins. Anyt12The Binding of Ligands to Proteins12.1INTRODUCTIONIn this chapter, we will discuss the binding of ligands to monomeric and oligomeric proteins. AnytGọi ngay
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