1-Chloro-2-hydroxy-3-butene (CHB) is an in vitro metabolite of 1,3-butadiene, a rodent/human carcinogen. To search for an approach detecting CHB in vivo, it is vital to obtain a full understanding of CHB metabolism. Previously, we demonstrated that CHB was bioactivated to 1-chloro-3-buten-2-one (CBO) by alcohol dehydrogenase. However, CHB metabolism by cytochrome P450s has not been reported. Thus, in the present study, CHB metabolism by rat liver microsomes was investigated. The results showed that CHB was converted to 1-chloro-3,4-epoxy-2-butanol (CEB) and CBO. 4-Methylpyrazole, a cytochrome P450 2E1-specific inhibitor, inhibited the formation of both CEB and CBO, while 1-benzylimidazole, a generic cytochrome P450 inhibitor, completely abolished the formation of CEB and CBO, suggesting that CHB metabolism was mediated by cytochrome P450s. Because the molecules have two chiral centers, CEB was detected as two stereoisomers, which were designated D-CEB and M-CEB, and were characterized as (2S,3R)-/(2R,3S)-CEB and (2R,3R)-/(2S,3S)-CEB, respectively. The amounts of M-CEB were more than those of D-CEB by 50–80%. The amounts of CEB and CBO increased linearly over time from 10 (or 20 min for CBO) to 50 min. CHB metabolism followed Michaelis-Menten kinetics; the K_m and V_max values were determined to be 6.4 ± 0.7 mM and 0.10 ± 0.01 nmol/min/mg protein for D-CEB, 4.2 ± 0.5 mM and 0.16 ± 0.01 nmol/min/mg protein for M-CEB, and 4.0 ± 0.5 mM and 4.6 ± 0.5 nmol/min/mg protein for CBO, respectively. Thus, CBO was the dominant product of CHB metabolism. Moreover, CEB was genotoxic at ≥ 50 μM as evaluated by the comet assay. Collectively, the data showed that CHB could be bioactivated to CEB and CBO by cytochrome P450s with CBO being the predominant product. Thus, the formation of CEB and CBO can be used as evidence of CHB production. The products may also play a role in toxicity of CHB.

1-氯-2-羟基-3-丁烯（CHB）是1,3-丁二烯（一种啮齿动物/人类致癌物）的体外代谢产物。为了寻找一种在体内检测CHB的方法，全面了解CHB代谢至关重要。以前，我们证明了CHB被乙醇脱氢酶生物激活为1-氯-3-丁烯-2-酮（CBO）。但是，尚未报道细胞色素P450引起的CHB代谢。因此，在本研究中，研究了大鼠肝微粒体对CHB的代谢作用。结果表明，CHB转化为1-氯-3,4-环氧-2-丁醇（CEB）和CBO。细胞色素P450 2E1特异性抑制剂4-甲基吡唑抑制CEB和CBO的形成，而通用细胞色素P450抑制剂1-苄基咪唑完全消除CEB和CBO的形成，表明CHB代谢由细胞色素P450介导。S，3 R）-/（2 R，3 S）-CEB和（2 R，3 R）-/（2 S，3 S）-CEB分别。M-CEB的含量比D-CEB的含量高50-80％。CEB和CBO的量随时间从10（对于CBO为20分钟）线性增加到50分钟。CHB代谢遵循Michaelis-Menten动力学；的ķ_米和V_最大对于D-CEB，测定值分别为6.4±0.7 mM和0.10±0.01 nmol / min / mg蛋白;对于M-CEB，测定值分别为4.2±0.5 mM和0.16±0.01 nmol / min / mg蛋白以及4.0±0.5 mM和4.6 CBO的蛋白质分别为±0.5 nmol / min / mg。因此，CBO是CHB代谢的主要产物。此外，通过彗星试验评估，CEB在≥50μM时具有遗传毒性。总体而言，数据表明，CHB可以被细胞色素P450生物激活为CEB和CBO，而CBO是主要产物。因此，CEB和CBO的形成可以用作CHB产生的证据。该产品还可能在CHB的毒性中起作用。