Oxygen is the most abundant element on the earth and is certainly one of the most important elements for life. Therefore, it has been a popular subject among biochemists since Lavoisier initiated the study of biological oxidative processes some 200 years ago. Nevertheless, very little is understood about how oxygen molecules are metabolized in the living organisms, because the principal developments in the field of biological oxidation have concerned the elucidation of pathways in which electrons are transferred from substrate through various carriers to molecular oxygen. The enzymes that catalyze dehydrogenation of primary sub-strates have been designated "dehydrogenases." In cases in which molecular oxygen serves as the immediate electron acceptor forming water or hydrogen peroxide, the enzymes have been called "oxidases." In 1955 evidence was obtained in several laboratories that oxygen may also play a more direct role in substrate oxidation. In a diverse group of reactions, including hydroxylations, cleavage of aromatic rings, and cyclization of steroids, the mechanism involves the direct addition of oxygen to the substrate. These reactions are catalyzed by specific enzymes which we proposed to name "oxygenases." During the last several years, oxygenases have been found to be distributed ubiquitously in animals, plants, and microorganisms and to play important roles in the metabolism of not only various aromatic and cyclic compounds but also of aliphatic compounds. The purpose of this book is to summarize our present knowledge of these enzymes and to further discuss and speculate on various possi-bilities as to the mechanism of this new type of enzymic reaction at a molecular level. In addition, attempts have been made to incorporate some recent developments concerning oxygen-carrying proteins, such as hemoglobin, myoglobin, hemerythrin, and hemocyanin. It is hoped that discussions on the mode of action of these oxygen-carrying proteins and cytochrome oxidases may contribute a great deal to the understanding of oxygen metabolism in general. ! Uwagi Oprawa nieznacznie zarysowana i wytarta. Brzegi stron lekko zakurzone. Pieczątki i adnotacje pobiblioteczne.