Molecular Mechanisms Of Oxygen Activation

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.

This monograph consists of manuscripts, summary statements, and poster abstracts submitted by invited speakers and poster contributors who participated in the symposium "Oxygen Complexes and Oxygen Activation by Transition Metals," held March 23-26, 1987, at Texas A&M University. This meeting was the fifth annual international symposium sponsored by the Texas A&M Industry-University Cooperative Chemistry Program (IUCCP). The co chairmen of the conference were Professors Arthur E. Martell and Donald T. Sawyer of the Texas A&M University Chemistry Department. The program was developed by an academic-industrial steering committee consisting of the co-chairmen and members appointed by the sponsoring chemical companies Dr. James F. Bradzil, The Standard Oil Company, Ohio; Dr. Jerry R. Ebner, Monsanto Company; Dr. Craig Murchison, Dow Chemical Company; Dr. Donald C. Olsen, Shell Development Company; Dr. Tim R. Ryan, Celanese Chemical Company; and Dr. Ron Sanderson, Texaco Chemical Company. The subject of this conference reflects the intense interest that has developed in academic institutions and industry on several aspects of dioxygen chemistry. These include the formation of dioxygen complexes and their applications in facilitated transport and oxygen separation; homo geneous and heterogeneous catalysis of oxidation; and oxygenation of organic substrates by molecular oxygen. The conference differs in two respects from several other symposia on dioxygen chemistry held during the past few years. First, there is extensive industrial participation, especially with respect to oxygen activation.

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

This presentation describes various aspects of the regulation of tissue oxygenation, including the roles of the circulatory system, respiratory system, and blood, the carrier of oxygen within these components of the cardiorespiratory system. The respiratory system takes oxygen from the atmosphere and transports it by diffusion from the air in the alveoli to the blood flowing through the pulmonary capillaries. The cardiovascular system then moves the oxygenated blood from the heart to the microcirculation of the various organs by convection, where oxygen is released from hemoglobin in the red blood cells and moves to the parenchymal cells of each tissue by diffusion. Oxygen that has diffused into cells is then utilized in the mitochondria to produce adenosine triphosphate (ATP), the energy currency of all cells. The mitochondria are able to produce ATP until the oxygen tension or PO2 on the cell surface falls to a critical level of about 4–5 mm Hg. Thus, in order to meet the energetic needs of cells, it is important to maintain a continuous supply of oxygen to the mitochondria at or above the critical PO2 . In order to accomplish this desired outcome, the cardiorespiratory system, including the blood, must be capable of regulation to ensure survival of all tissues under a wide range of circumstances. The purpose of this presentation is to provide basic information about the operation and regulation of the cardiovascular and respiratory systems, as well as the properties of the blood and parenchymal cells, so that a fundamental understanding of the regulation of tissue oxygenation is achieved.

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.

Comprehensive Natural Products III, Third Edition, Seven Volume Set updates and complements the previous two editions, including recent advances in cofactor chemistry, structural diversity of natural products and secondary metabolites, enzymes and enzyme mechanisms and new bioinformatics tools. Natural products research is a dynamic discipline at the intersection of chemistry and biology concerned with isolation, identification, structure elucidation, and chemical characteristics of naturally occurring compounds such as pheromones, carbohydrates, nucleic acids and enzymes. This book reviews the accumulated efforts of chemical and biological research to understand living organisms and their distinctive effects on health and medicine and to stimulate new ideas among the established natural products community. Provides readers with an in-depth review of current natural products research and a critical insight into the future direction of the field Bridges the gap in knowledge by covering developments in the field since the second edition published in 2010 Split into 7 sections on key topics to allow students, researchers and professionals to find relevant information quickly and easily Ensures that the knowledge within is easily understood by and applicable to a large audience