Cytochromes P450

Cytochromes P450 (CYPs) comprise a large superfamily of proteins that are of central importance in the detoxification or activation of a tremendous number of natural and synthetic hydrophobic xenobiotics, including many therapeutic drugs, chemical carcinogens and environmental pollutants. CYPs are important in mediating interactions between an organism and its chemical environment and in the regulation of physiological processes. Cytochrome P450 Protocols, Third Edition focuses on high-throughput methods for the simultaneous analysis of multiple CYPs, substrates or ligands. Although the emphasis is on CYPs of mammalian origin, it reflects an increasing interest in CYPs of bacterial species. Also included are chapters on cytochrome P450 reductase (the redox partner of CYPs) and the flavin-containing monooxygenases (FMOs), and metabolomic and lipidomic approaches for identification of endogenous substrates of CYPs (‘de-orphanizing’ CYP substrates). Written in the successful Methods in Molecular BiologyTM series format, chapters include introductions to their respective topics, lists of the necessary materials and reagents, step-by-step, readily reproducible protocols, and notes on troubleshooting and avoiding known pitfalls. Authoritative and easily accessible, Cytochrome P450 Protocols, Third Edition provides a wide range of techniques accessible to researchers in fields as diverse as biochemistry, molecular biology, pharmacology, toxicology, environmental biology and genetics.

Cytochromes P450: Metabolic and Toxicological Aspects examines cytochrome P450 proteins and their role in toxicity/carcinogenicity and the metabolism of foreign chemicals. Studying the function of these proteins enables us to: Predict the pathways and outcome of chemical metabolism to rationalize species, sex, and age differences in toxicity Anticipate drug interactions Modify doses to fit the needs of patients Contributions from internationally acknowledged experts are organized into three sections. The first section provides an overview, the next profiles each of the cytochrome P450 families and subfamilies involved in chemical metabolism, and the last section discusses new issues and developments of current interest. This detailed and thorough examination of cytochrome P450 will be a useful source for research scientists, especially those working in the pharmaceutical industry, dealing with the safety evaluation of chemicals and the study of their metabolism, pharmacokinetics, and toxicological properties.

With contributions by a team of internationally respected scientists, this book provides up-to-date information on the extensively studied cytochrome P450 enzyme in a very accessible manner.

Cytochrome P450: Structure, Mechanism, and Biochemistry, third edition is a revision of a review that summarizes the current state of research in the field of drug metabolism. The emphasis is on structure, mechanism, biochemistry, and regulation. Coverage is interdisciplinary, ranging from bioinorganic chemistry of cytochrome P450 to its relevance in human medicine. Each chapter provides an in-depth review of a given topic, but concentrates on advances of the last 10 years.

During half a century, cytochrome P450 in its original uniqueness as an optically "wrong" cytochrome has attracted many investigators, who have contributed to the unveiling of a bewildering multiplicity of biologically important functions of the, by now very large, superfamily of cytochrome P 450 enzymes. With its discovery in 1958 and with the advent of more refined spectroscopic methodologies, through the double wavelength spectrophotometry, the mysterious enzyme system began to reveal its secrets in a swift stream of investigative successes. As one of the most extensively studied enzyme systems worldwide the interest in cytochromes P450 very much reflects its importance in the elimination of drugs and other chemicals from the body and its role in chemical toxicity and in the aetiology of diseases such as cancer. There has been significant progress in research in this area in recent years and current books on this subject are now out of date. This much needed, new, fully up-to-date publication fills this gap and emphasises the new relevant topics that have emerged during the last decade in an easily accessible manner. The enzyme system, cytochromes P450, comprises a number of families/subfamilies, and the focus of the book is to deal with each individually, furnishing information directly relevant to scientists involved in the development of chemicals, in particular in the evaluation of their safety. The book has contributions from internationally respected scientists who are research-active in the relevant areas. The authors have made extensive use of figures and tables so that the reader can access the necessary information without always having to read the text. In addition, a very extensive, user-friendly index is a unique hallmark of the book. Part A of this monograph introduces the reader to the current knowledge of the evolutionary development of cytochrome P450 structure and function. Furthermore, it deals with the role of this enzyme in the formation of reactive intermediates. The shrewd and extensive utilisation of the molecular biology methodology very rapidly led to a vast body of enzymes calling for a classification of the plethora of different cytochromes P450 (the superfamily) into families and subfamilies. This is aptly exemplified by the ten chapters in Part B of this book, dealing with ten subfamilies and two families of cytochrome P450. Part C offers an insight into another aspect of cytochrome P450 research, namely its regulation through receptor-mediated stimuli - as opposed to enzyme induction or inhibition. The final chapter translates the current data on one of several drug metabolising systems into clinical application and highlights the role of cytochromes P450 in the treatment of neoplastic growth. The book deals extensively with each family/subfamily of the cytochromes P450 that contribute to the metabolism of xenobiotics. Essential and invaluable information is provided for the industrial research scientist working with fine chemicals, and especially those in the pharmaceutical industry, dealing with the safety evaluation of chemicals or being involved in the study of their metabolism, pharmacokinetics and toxicological properties. It should also prove of interest to Regulators concerned with the safety evaluation of chemicals, research pharmacologists and toxicologists, and postgraduate students studying drug metabolism and toxicology at an advanced level.

Cytochromes are coloured iron-containing proteins that transfer electrons during cellular respiration and photosynthesis. The Cytochrome P450 family of enzymes catalyze reactions whereby water-insoluble drugs or metabolites, that would otherwise reach toxic levels in cell membranes, are rendered suitably water-soluble to leave the cell and be excreted in the urine. Due to the extensive nature of this subject, which is an area of intense scientific interest, the field is rapidly advancing and there is a need for new textbooks to keep abreast of the latest developments. The book fulfils that role in providing a fast-track approach for those coming into the P450 field, either at postgraduate level or in particular within the pharmaceutical industry. A Guide to Cytochrome P450 Structure and Function acts as an adjunct to the previous book Cytochromes P450: Structure, Function and Mechanism. It reviews the current status of the P450 field in terms of our present knowledge and understanding of the enzymes structure and function, including their multiplicity of forms, diversity of substrates, and selectivity. This is brought together with the latest research topics, including pharmacogenetics, regulation, human DMEs, toxicity screening and molecule modeling, to provide a fast-track approach for those new to the field.

In the ten years that have elapsed since the first edition of this book went to press, the cytochrome P450 field has completed the transition to a discipline in which structure and mechanism, even regulation and biological function, are dealt with in molecular terms. The twin forces that have propelled this remarkable progress have been the widespread adoption of molecular biological approaches and the successful application of modem structural techniques. Only a few P450 primary sequences were available in 1985, whereas hundreds of P450 sequences are now available. Site-specific mutagenesis was then mostly a proverbial gleam in the eye of the P450 community, but it is now a standard technique in the research repertoire. The first crystal structure of a cytochrome P450 enzyme had just been solved in 1985 and appeared on the cover of the first edition. Today, the high-reso lution crystal structures of four soluble bacterial P450 enzymes are available and the race is on to develop approaches that will permit us to determine the structures of the membrane-bound forms of the enzyme. The past ten years has seen phenomenal progress let us hope that the next ten will prove equally exciting. The book is informally divided into four sections. In order to hold the book close to the advancing front of research, some of the chapter topics from the first edition have been dropped to make room for new or expanded topics.