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Competitive inhibition is a form of enzyme inhibition where binding of the inhibitor to the active site on the enzyme prevents binding of the substrate and ''vice versa''.〔(【引用サイトリンク】url=http://assay.nih.gov/assay/index.php/Types_of_Inhibition )〕〔(【引用サイトリンク】url=http://cti.itc.virginia.edu/~cmg/Demo/compInh.html )〕 Most competitive inhibitors function by binding reversibly to the active site of the enzyme.〔 As a result, many sources state that this is the defining feature of competitive inhibitors.〔(【引用サイトリンク】url=http://dl.clackamas.cc.or.us/ch106-08/enzyme1.htm )〕 This, however, is a misleading oversimplification, as there are many possible mechanisms by which an enzyme may bind either the inhibitor or the substrate but never both at the same time.〔 For example, allosteric inhibitors may display competitive, non-competitive, or uncompetitive inhibition.〔 ==Mechanism== In competitive inhibition, at any given moment, the enzyme may be bound to the inhibitor, the substrate, or neither, but it cannot bind both at the same time. In virtually every case, competitive inhibitors bind in the same binding site as the substrate, but same-site binding is not a requirement. A competitive inhibitor could bind to an allosteric site of the free enzyme and prevent substrate binding, as long as it does not bind to the allosteric site when the substrate is bound. For example, strychnine acts as an allosteric inhibitor of the glycine receptor in the mammalian spinal cord and brain stem. Glycine is a major post-synaptic inhibitory neurotransmitter with a specific receptor site. Strychnine binds to an alternate site that reduces the affinity of the glycine receptor for glycine, resulting in convulsions due to lessened inhibition by the glycine. In competitive inhibition, the maximum velocity () of the reaction is unchanged, while the apparent affinity of the substrate to the binding site is decreased (the dissociation constant is apparently increased). The change in (Michaelis-Menten constant) is parallel to the alteration in . Any given competitive inhibitor concentration can be overcome by increasing the substrate concentration in which case the substrate will outcompete the inhibitor in binding to the enzyme. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Competitive inhibition」の詳細全文を読む スポンサード リンク
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