酶促反應(yīng)動(dòng)力學(xué)ppt課件-文庫吧資料
2025-02-27 15:39本頁面
【正文】 n be reached at saturating substrate concentration, or when [S] So MM equation can be rewritten as: ?? ?? ?mKSSvv?? m a x? ? ? ?m a x2][2][ 1 vEkEkv tSKtSm??????Enzymecatalyzed rate is saturated Understanding Km ? Km is a constant derived from rate constants ? Km is, under true MichaelisMenten conditions, an estimate of the dissociation constant of E from S, because at equilibrium, Reversible reaction, dissociation constant is So small Km means tight substrate binding。 3) Rate law. PEESSE ??k1 K1 k2 K2 Initial Velocity Assumption ? In the beginning of the reaction, there is very little product, or [P] is small. So the amount of [ES] contributed by E+P is negligible. ? Thus, the MM equation concerns the reaction rate that is measured during early reaction period. ? In which case, the enzyme catalyzed reaction can be modified to: ? K1 PEESSE ??k1 K1 k2 PEESSE ??k1 k2 K2 Rate Law in Enzyme Catalyzed Reactions ? Rate law still applies in enzyme catalyzed reactions. ? The forward velocity, or rate, vf is, ? The reverse velocity or rate, or the rate of disappearance vd is, ? At steady state, there is no accumulation of [ES], thus: PEESSE ??k1 K1 k2 ? ?? ?SEkv f 1?? ? ? ? ? ?ESkkESkESkv d )( 2121 ???? ??df vv ?Derivation of MichaelisMenten Equation ? We need one more condition, that is, the total enzyme concentration, [Et] is the sum of that of enzymesubstrate plex, [ES], and that of free enzyme, [E]: ? At steady state, the forward rate should equal to the reverse rate: ? Rate of production formation (rate law), v = k2[ES]. So: ? ? ? ? ? ? ? ? ? ?? ? ? ?? ? ? ?? ? ? ?? ? ? ? ? ?? ? ? ? ? ?? ? ? ?? ?? ?? ?? ?? ?? ? ? ?? ?? ? mtkkkKttttttKSSEESkkkSSEkkSkSEkESkkSkESSEkESkkSESkEkESkkSESkSEkESkkSESEkm?????? ??
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