Human enzymes of xenobiotic metabolism

人体异源代谢酶异源生物是药物、致癌物和污染物等外来化学品。外来化合物在人体内以惊人的化学方式代谢。在细胞色素P450和谷胱甘肽转移酶等酶的催化下，这些代谢过程在确定化学品的毒性效应方面可能是至关重要的。因此，他们不仅对生物化学感兴趣，而且对药理学和毒理学的相关学科也很感兴趣。Josephy博士研究的中心主题是了解催化外源生物新陈代谢的酶的生物化学，特别关注它们的蛋白质结构和催化功能。他的实验室。将两种不同的生物技术结合在一起：细菌诱变性检测和重组蛋白表达。在约瑟芬博士的实验室开发的新检测系统中，大肠杆菌被用来检测化学诱变剂，它们还被“教导”以与人类相同的方式代谢外来化学物质。也就是说，人类的酶在细菌细胞内以重组蛋白的形式表达。这种方法导致了对有毒化学物质的越来越可靠和相关的分析，它还提供了对重要人类酶的作用机制的洞察。通过基因组测序项目发现的这些人类基因/酶中自然发生的变异的功能效应现在正在研究中。另一种研究途径是在实验室中对序列和催化活性发生变化的酶进行“进化”。研究计划的这一方面是通过随机诱变编码酶的基因，然后使用诱变试验来筛选突变体文库并鉴定具有改变活性的突变体。

Human enzymes of xenobiotic metabolismXenobiotics are foreign chemicals such as drugs, carcinogens, and pollutants. Foreign compounds are metabolized in the human body in chemically remarkable ways. These metabolic processes, catalyzed by enzymes such as cytochrome P450 and glutathione transferase, can be crucial in determining the toxic effects of chemicals. Therefore, they are of great interest not only in biochemistry but also in the allied disciplines of pharmacology and toxicology. The central theme of Dr. Josephy's research is understanding the biochemistry of the enzymes that catalyze the metabolism of xenobiotics, with particular attention to their protein structures and catalytic functions. His lab. has brought together two different biotechnologies: bacterial mutagenicity assays and recombinant protein expression. In the new assay systems developed in Dr. Josephy's lab., E. coli bacteria are used to detect chemical mutagens, and they are also "taught" to metabolize foreign chemicals in the same ways that humans do. That is, human enzymes are expressed as recombinant proteins within the bacterial cells. This approach has led to increasingly reliable and relevant assays for toxic chemicals, and it also provides insight into the mechanisms of action of important human enzymes. The functional effects of naturally occurring variations in these human genes/enzymes, which are being discovered via genome sequencing projects, are now being studied. Another avenue of research is the "evolution", in the laboratory, of enzymes with altered sequences and catalytic activities. This aspect of the research program is pursued by randomly mutagenizing the gene encoding the enzyme, and then using the mutagenicity assay to screen libraries of mutants and identify ones with altered activities.