Cytochrome P450 (CYP) enzymes are one of the largest protein families, and they metabolise a wide range of lipophilic organic endogenous and exogenous compounds. Many cytochrome P450 genes have been cloned and characterised, and they are frequently used as biomarkers in environmental toxicology studies because of their sensitivity and inducibility. In the present study, the full-length cDNAs of DpCYP370B and DpCYP4 were cloned from Daphnia pulex for the first time. The sequence of DpCYP370B consisted of an ORF of 1515 bp that encoded a 504 amino acid polypeptide, while the sequence of DpCYP4 comprised an ORF of 1527 bp that encoded a 508 amino acid polypeptide. Homologous alignments revealed the presence of a conserved cysteine haeme-iron ligand signature, FxxGxxxCxG, located in the C-terminal portion. Both the proteins contained a sequence for a transmembrane region that was deduced to be located in the endoplasmic reticulum. Subsequently, the expression levels of DpCYP370B and DpCYP4, as well as those of CYP4AN1, CYP4C33, and CYP4C34, were investigated using quantitative real-time PCR after exposure to five polystyrene nanoplastic concentrations: 0 (control), 0.1, 0.5, 1, and 2 mg/L for 21 days. Except for DpCYP4, the highest mRNA expression was observed at 0.5 mg/L nanoplastics; next, the expression of three of the enzymes (DpCYP370B, CYP4AN1, CYP4C34,) decreased to that of the control level at 1 and 2 mg/L doses of nanoplastics. The expression of DpCYP4 did not significantly change compared with that of the control group. These results indicated that CYP genes might play an important role in protecting D. pulex against nanoplastic pollutants.

中文翻译：

---

水蚤（Daphnia pulex）中细胞色素P450酶的分子特征及其通过聚苯乙烯纳米塑料的表达调控。

细胞色素P450（CYP）酶是最大的蛋白质家族之一，它们可代谢多种亲脂性有机内源性和外源性化合物。已经克隆并鉴定了许多细胞色素P450基因，由于它们的敏感性和可诱导性，它们经常在环境毒理学研究中用作生物标记。在本研究中，首次从水蚤（Daphnia pulex）克隆了DpCYP370B和DpCYP4的全长cDNA。DpCYP370B的序列由编码504个氨基酸的多肽的1515bp的ORF组成，而DpCYP4的序列由编码508个氨基酸的多肽的1527bp的ORF组成。同源比对揭示了位于C末端部分的保守的半胱氨酸血红素-铁配体标记FxxGxxxCxG的存在。两种蛋白质都包含一个跨膜区域的序列，该序列被推定为位于内质网中。随后，在暴露于5种聚苯乙烯纳米塑料浓度：0（对照），0.1、0.5、1和0的聚苯乙烯纳米塑料浓度后，使用定量实时PCR研究了DpCYP370B和DpCYP4以及CYP4AN1，CYP4C33和CYP4C34的表达水平。 2 mg / L，持续21天。除DpCYP4外，在0.5 mg / L纳米塑料中观察到最高的mRNA表达。接下来，三种酶（DpCYP370B，CYP4AN1，CYP4C34）的表达在1和2 mg / L剂量的纳米塑料中均降至对照水平。与对照组相比，DpCYP4的表达没有明显改变。这些结果表明CYP基因可能在保护D中起重要作用。