生化工程,第二章酶促反應(yīng)動力學(xué)(參考版)
2025-02-19 23:57本頁面
【正文】 (d) dependence of K on [A].88Differentiation Between Mechanisms謝謝觀看 /歡迎下載BY FAITH I MEAN A VISION OF GOOD ONE CHERISHES AND THE ENTHUSIASM THAT PUSHES ONE TO SEEK ITS FULFILLMENT REGARDLESS OF OBSTACLES. BY FAITH I BY FAITH。 (b) dependence of K on [B]。 (d) dependence of K on [B]83II. Ordered sequential mechanisms 順序機(jī)制8485III. pingpong mechanisms底物 A和 B始終不同時與酶結(jié)合。 (b) dependence of K on [A]。試求：方程表示。 Ea 是反應(yīng)活化能 (kcal/mol). R 是氣體常數(shù) T 是絕對溫度， A是前因子752. 熱失活作用 (下降區(qū) ). (酶的熱變性作用 )酶的熱變性失活符合一級反應(yīng)動力學(xué)方程：式中 [E0] 酶的初始濃度 。這是由于溫度升高，雖然可加速酶的催化反應(yīng)速率，同時也加快了酶的熱失活速率。pHactivity profiles of two enzymes. (A)胃蛋白酶 。根據(jù) 解離常數(shù) 的定義和酶的質(zhì)量守恒可得：70消除 [E] 和 [EH2+] 項(xiàng)，可得到：令 得到 ,即 ,71For CASE II (Ionic Substrate)The reaction scheme is as follow:Similarly, we can get, where SH+ + ES + H+ESH+Km39。Ionic formModifies Reaction rateChanges Enzyme activityInfluences 67For CASE I (Ionic Enzyme):The reaction scheme is as follow:Where the meanings of the denotations are:l EH: active forml E, EH2+: inactive forml E: deprotonation forml EH2+: protonation form68With similar analysis and derivations as before, we can get,where69 考慮到酶發(fā)揮最佳的活力狀態(tài)是 EH，最佳 pH應(yīng)該是唯一的，而在最佳 pH時， EH的濃度應(yīng)該達(dá)到最大 。 Allosteric EnzymeThe rate expression:where n is the cooperativity coefficient(協(xié)同系數(shù) ), and n1 indicates positive cooperativity. （ 1－ ）By rearranging, we have,Hill 方程實(shí)例： 血紅蛋白 63Plots on Allosteric Enzymes雙曲線S形曲線6465影響酶催化反應(yīng)速率的因素影響酶催化反應(yīng)速率的因素影響酶催化反應(yīng)速率的因素有很多，它們會影響到酶的結(jié)構(gòu)或化學(xué)狀態(tài)。? 如：已糖激酶、血紅蛋白 (參見王鏡巖， 《 生物化學(xué) 》 第三版，第 259266頁。這類酶具有別構(gòu)部位和活性部位。E + S [ES] + SE + P[ESS]Km’KSIk+253With similar equations and derivations as before, 變換方程得：Then,we can get,54when , .Namely , then or Namely , then or Discussions about Substrate Inhibitionsl The substrate concentration at which the maximum reaction rateachieves can be obtained by setting , and we can get,l Low substrate concentrationThe origin MichaelisMenten equation obtained, thus no inhibition observed.l High substrate concentrationThe inhibition effect is dominant.55At low substrate concentration, the rate expression approximates to the MichaelisMenten equation, then the curve in doublereciprocal plot is parallel with the linear line d
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