Measurement of cysteine S-conjugate β-lyase activity.
Measurement of cysteine S-conjugate β-lyase activity.
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半胱氨酸S-缀合物β-裂解酶活性的测量。
DOI：
10.1002/0471140856.tx0436s44
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
Bruschi,SamA
中科院分区：
文献类型：
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作者：
Cooper,ArthurJL;Krasnikov,BorisF;Pinto,JohnT;Bruschi,SamA
半胱氨酸S-缀合物β-裂合酶是含有吡哆醛5′-磷酸(PLP)的酶，可催化半胱氨酸S-缀合物[RSCH2CH(NH3+)CO2−]和硒Se-缀合物[RSeCH2CH(NH3+)CO2−]转化为丙酮酸、铵和含硫片段(RSH)或在β位含有离去基团分别是含硒片段（RSeH）。在哺乳动物中，至少有十种 PLP 酶催化与此类半胱氨酸 S-缀合物的 β-消除反应。所有这些酶都是参与氨基酸代谢的酶，通常不催化 β-裂合酶反应，而是催化非生理性 β-裂合酶副反应，该副反应取决于 –SR 或 –SeR 部分的吸电子特性。对于半胱氨酸S-缀合物，如果消除的RSH是稳定的，则该化合物可能被S-硫甲基化并排出（硫甲基分流）或S-葡萄糖醛酸化并无害地排出。然而，如果 RSH 具有化学反应性，则半胱氨酸 S-缀合物可能因 β-裂合酶反应而有毒。半胱氨酸S-结合β-裂合酶途径引起了毒理学家的特别兴趣，因为它涉及卤代烯烃和某些药物的生物活化（毒性）。该单元提供了半胱氨酸S-缀合物β-裂合酶活性分析的方案。Curr。协议。毒性。 44：4.36.1-4.36.18。 © 2010 John Wiley & Sons, Inc. 版权所有
CysteineS‐conjugate β‐lyases are pyridoxal 5′‐phosphate (PLP)–containing enzymes that catalyze the conversion of cysteineS‐conjugates [RSCH2CH(NH3+)CO2−] and seleniumSe‐conjugates [RSeCH2CH(NH3+)CO2−] that contain a leaving group in the β position to pyruvate, ammonium and a sulfur‐containing fragment (RSH) or selenium‐containing fragment (RSeH), respectively. In mammals, at least ten PLP enzymes catalyze β‐elimination reactions with such cysteineS‐conjugates. All are enzymes involved in amino acid metabolism that do not normally catalyze a β‐lyase reaction, but catalyze a non‐physiological β‐lyase side‐reaction that depends on the electron‐withdrawing properties of the –SR or –SeR moiety. In the case of cysteineS‐conjugates, if the eliminated RSH is stable, the compound may beS‐thiomethylated and excreted (thiomethyl shunt) orS‐glucuronidated and harmlessly excreted. However, if RSH is chemically reactive, the cysteineS‐conjugate may be toxic as a result of the β‐lyase reaction. The cysteineS‐conjugate β‐lyase pathway is of particular interest to toxicologists because it is involved in the bioactivation (toxification) of halogenated alkenes and certain drugs. This unit provides protocols for the analysis of cysteineS‐conjugate β‐lyase activity.Curr. Protoc. Toxicol. 44:4.36.1‐4.36.18. © 2010 by John Wiley & Sons, Inc.