CYTOCHROME-P-450 ISOZYME SELECTIVITY IN THE OXIDATION OF ACETAMINOPHEN
CYTOCHROME-P-450 ISOZYME SELECTIVITY IN THE OXIDATION OF ACETAMINOPHEN
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DOI：
10.1021/tx00001a009
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发表时间：
1988-01-01
影响因子：
4.1
通讯作者：
NELSON, SD
中科院分区：
文献类型：
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作者：
HARVISON, PJ;GUENGERICH, FP;NELSON, SD
高度纯化的细胞色素P-450同工酶催化对乙酰氨基酚（APAP）形成3-谷胱甘肽-S-基对乙酰氨基酚（GS-APAP）和3-羟基对乙酰氨基酚（3-OH-APAP）。未处理雄性大鼠的一种主要同工酶（P-450 UT-A）催化ca. 2.0 nmol/nmol的P-450/10 min的3-OH-APAP和约7.2 nmol的GS-APAP/nmol的P-450/10 min。细胞色素P-450 UT-A的特异性抗体引起微粒体孵育中产生的两种代谢物的量减少。与这些结果相反，从大鼠肝脏，细胞色素P-450 UT-F和女性特异性同工酶P-450 UT-I的其他两个组成的P-450同工酶，产生较少的氧化代谢产物。此外，它们产生的儿茶酚代谢物显著多于谷胱甘肽结合物。这些结果与雄性大鼠比雌性大鼠更易受到对乙酰氨基酚肝毒性的观察结果雅阁。苯巴比妥诱导的同工酶也产生了更多的儿茶酚比谷胱甘肽结合物。相反，由β-葡聚糖诱导的主要同工酶与3-OH-APAP相比，细胞色素P-450 β NF-B-萘酚酮产生显著更大量的GS-APAP。当与主要的苯巴比妥诱导型（细胞色素P-450 PB-B）进行比较时，观察到两种代谢产物形成的明确同工酶特异性。细胞色素P-450 PB-B和P-450 β NF-B分别以2.21和0.53 nmol/nmol P-450/10分钟的速率形成儿茶酚。另一方面，细胞色素P-450 PB-B每10分钟产生1.62 nmol/nmol的P-450 GS-ASAP，而细胞色素P-450 β NF-B每10分钟产生4.26 nmol/nmol的P-450。这些结果表明3-OH-APAP和GS-APAP主要由不同的中间体产生。此外，在用细胞色素P-450 β NF-B进行的单次转换实验中直接检测到细胞色素P-450氧化APAP中的反应性中间体N-乙酰基-对苯醌亚胺（NAPQI），而细胞色素P-450 PB-B形成的量低于测定的检测限。
Highly purified isozymes of cytochrome P-450 catalyzed the formation of 3-glutathion-S-ylacetaminophen (GS-APAP) and 3-hydroxyacetaminophen (3-OH-APAP) from acetaminophen (APAP). A major isozyme from untreated male rats (P-450UT-A) catalyzed the formation of ca. 2.0 nmol/nmol of P-450/10 min of 3-OH-APAP and approximately 7.2 nmol of GS-APAP/nmol of P-450/10 min. Antibodies specific for cytochrome P-450UT-A caused a decrease in the amounts of both metabolites produced in microsomal incubations. In contrast to these results, two other constitutive P-450 isozymes from rat liver, cytochrome P-450UT-F and the female specific isozyme P-450UT-I, produced less of both oxidative metabolites. Moreover, they produced significantly more of the catechol metabolite than the glutathione conjugate. These results are in accord with the observation that male rats are more susceptible to acetaminophen hepatotoxicity than female rats. Isozymes induced by phenobarbital also produced more of the catechol than the glutathione conjugate. Conversely, the major isozyme induced by .beta.-naphthoflavone, cytochrome P-450.beta.NF-B, produced a significantly greater amount of GS-APAP than 3-OH-APAP. When comparison was made to a major phenobarbital inducible form (cytochrome P-450PB-B) a definite isozyme specificity for the formation of the two metabolites was seen. The catechol was formed at rates of 2.21 and 0.53 nmol/nmol of P-450/10 min by cytochromes P-450PB-B and P-450.beta.NF-B, respectively. On the other hand, cytochrome P-450PB-B produced 1.62 nmol/nmol of P-450/10 min of GS-ASAP versus 4.26 nmol/nmol of P-450/10 min for cytochrome P-450.beta.NF-B. These results show that 3-OH-APAP and GS-APAP arise primarily from different intermediates. Furthermore, a reactive intermediate in the oxidation of APAP by cytochrome P-450, N-acetyl-p-benzoquinone imine (NAPQI), was directly detected in single turnover experiments with cytochrome P-450.beta.NF-B, whereas the amount formed by cytochrome P-450PB-B was below the limits of detection for the assay.