The aromatic amino acid hydroxylases phenylalanine hydroxylase (PheH), tyrosine hydroxylase (TyrH) and tryptophan hydroxylase (TrpH) utilize tetrahydropterin and molecular oxygen to catalyze aromatic hydroxylation. All three enzymes have similar active sites and contain an iron atom facially coordinated by two histidines and a glutamate. The three enzymes also catalyze the benzylic hydroxylation of 4- methylphenylalanine. The intrinsic primary and?-secondary isotope effects for benzylic hydroxylation and their temperature dependences are nearly identical for the three enzymes, suggesting that the transition states, the tunneling contributions and the reactivities of the iron centers are the same. When molecular oxygen and the tetrahydropterin are replaced by hydrogen peroxide (H2O2), these enzymes catalyze the hydroxylation of phenylalanine to form tyrosine and meta-tyrosine with nearly identical second order rate constants. When the H2O2-dependent reaction is carried out with cyclohexylalanine or 4-methylphenylalanine, the products are 4-HO-cyclohexylalanine and 4-hydroxymethylphenylalanine, respectively. These experiments provide further evidence that the intrinsic reactivities of the iron centers in these enzymes are the same. Wild-type PheH and the uncoupled mutant protein V379D exhibit normal and inverse isotope effects, respectively, with deuterated phenylalanines. When the reaction is monitored by stopped-flow absorbance spectroscopy, three steps are visible. The first step is the reversible binding of O2, the second step is 5-7 fold faster than the turnover number, setting a limiting value for the rate constant for O2 activation, and the last step is non-enzymatic. There is no burst in the pre-steady state formation of tyrosine. These results are consistent with formation of the new C-O bond to form tyrosine as the ratelimiting step of the reaction. The reaction of TrpH with both tryptophan and phenylalanine was studied by stopped-flow absorbance spectroscopy and rapid-quench product analysis. With either amino acid as substrate, four steps can be distinguished. The first step is the reversible binding of O2 to the Fe(II) center; this results in an absorbance signature with a maximum at 420 nm. This O2 complex decays with a rate constant that is 18-22 fold faster than the turnover number with either amino acid, setting a the lower limit for the rate constant for O2 activation. The rate constant for the third step agrees well with the pre-steady state of formation of 5-hydroxytryptophan or tyrosine from rapid-quench product analysis. The rate constant for the fourth step agrees well with the turnover number. Overall, these results show that O2 activation is fast and turnover with each amino acid is limited by hydroxylation and release of a product, with the former step being about 4-fold faster than the latter.

Molecular Mechanisms of Oxygen Activation reviews some of the major advances that have been made in our understanding of the molecular mechanisms underlying oxygen activation, with emphasis on the role of oxygen activation in contemporary biological processes. The biological role of oxygenases in the metabolism of fatty acids and steroids is discussed, along with the functions of heme-containing dioxygenases, a-ketoglutarate-coupled dioxygenases, and pterin-requiring aromatic amino acid hydroxylases. This book is comprised of 14 chapters and begins with an overview of the general properties and biological functions of oxygenases, along with the chemical aspects of oxygen fixation reactions. The reader is then introduced to research concerning fatty acid and steroid oxygenases which has appeared in the literature since 1962, paying particular attention to the mechanism of oxygenation and the biosynthesis and metabolism of steroids. Subsequent chapters explore the biological functions of a variety of oxygenases such as heme-containing dioxygenases, copper-containing oxygenases, flavoprotein oxygenases, and pterin-requiring aromatic amino acid hydroxylases. Superoxide dismutase, cytochrome c oxidase, peroxidase, and bacterial monoxygenases are also considered. This monograph should serve as a valuable reference for biochemists as well as undergraduate and graduate students of biochemistry.

Oxygenases focuses on the processes, methodologies, technologies, and approaches involved in oxygenases, including its distribution in animals, plants, and microorganisms and its role in the metabolism of aromatic, cyclic, and aliphatic compounds. The selection first offers information on the history and scope of oxygenases, methodology of oxygen isotopes, and phenolytic oxygenases. Discussions focus on the separation and purification of compounds for isotopic analysis; general properties and mechanisms of action of oxygenases; physiological significance of oxygenases; dehydrogenases, oxidases, and oxygenases; and problems and restrictions in the use of oxygen-18. The text then examines aromatic hydroxylations, oxygenases in lipid and steroid metabolism, and bacterial oxidation of hydrocarbons. Topics include anaerobic oxidation of alkanes, involvement of molecular oxygen in hydrocarbon utilization, steroid hydroxylation mechanisms, oxygenases in the biosynthesis of steroid hormones, conversion of dopamine to norepinephrine, and general discussion of mechanism of aerobic hydroxylation reactions. The selection is a valuable reference for researchers interested in the process of oxygenases.

The field of isotope effects has expanded exponentially in the last decade, and researchers are finding isotopes increasingly useful in their studies. Bringing literature on the subject up to date, Isotope Effects in Chemistry and Biology covers current principles, methods, and a broad range of applications of isotope effects in the physical, biolo

A Comprehensive Guide to Crucial Attributes of Therapeutic Proteins in Biological Pharmaceuticals With this book, Dr. Raju offers a valuable resource for professionals involved in research and development of biopharmaceutical and biosimilar drugs. This is a highly relevant work, as medical practitioners have increasingly turned to biopharmaceutical medicines in their search for safe and reliable treatments for complex diseases, while pharmaceutical researchers seek to expand the availability of biopharmaceuticals and create more affordable biosimilar alternatives. Readers receive a thorough overview of the major co-translational modifications (CTMs) and post-translational modifications (PTMs) of therapeutic proteins relevant to the development of biotherapeutics. The majority of chapters detail individual CTMs and PTMs that may affect the physicochemical, biochemical, biological, pharmacokinetic, immunological, toxicological etc. properties of proteins. In addition, readers are guided on the methodology necessary to analyze and characterize these modifications. Thus, readers gain not only an understanding of CTMs/PTMs, but also the ability to design and assess their own structure-function studies for experimental molecules. Specific features and topics include: Discussion of the research behind and expansion of biopharmaceuticals Twenty chapters detailing relevant CTMs and PTMs of proteins, such as glycosylation, oxidation, phosphorylation, methylation, proteolysis, etc. Each chapter offers an introduction and guide to the mechanisms and biological significance of an individual CTM or PTM, including practical guidance for experiment design and analysis An appendix of biologic pharmaceuticals currently on the market, along with an assessment of their PTMs and overall safety and efficacy This volume will prove a key reference on the shelves of industry and academic researchers involved in the study and development of biochemistry, molecular biology, biopharmaceuticals and proteins in medicine, particularly as biopharmaceuticals and biosimilars become ever more prominent tools in the field of healthcare.

Mononuclear iron containing enzymes are important intermediates in bioprocesses and have potential in the industrial biosynthesis of specific products. This book features topical review chapters by leaders in this field and its various sub-disciplines.

The Enzymes, Volume 47, highlights new advances in the field, with this new volume presenting interesting chapters on The Multipurpose Family of Oxidases, Vanillyl alcohol oxidase, Choline oxidases, Aryl alcohol oxidase, D- and L-amino acid oxidases, Sugar oxidases, Phenolic Compounds hydroxylases, Baeyer-Villiger Monooxygenases, Flavin-dependent halogenases, Flavin-dependent dehalogenases, Styrene Monooxygenases, Bacterial luciferases, Cellobiose Dehydrogenases, Prenylated flavoenzymes, Ene-reductases, Flavoenzymes in Biocatalysis. - Provides the authority and expertise of leading contributors from an international board of authors - Presents the latest release in The Enzymes series