Advances in Cancer Research 6. [antikvár]

I. Introduction The recognition and description of the enzymes that mediate the various steps in the intermediary metabolic sequences in tissues have constituted one of the great advances in biochemistry during the past 30 years. Many of the studies involved in this development were performed on unicellular organisms and animal tissues, but by the doctrine of the unity of biochemistry were assumed to apply to man. If metabolic processes and the associated enzyme activities in tissues could be reflected in the blood of man, the ready and repeated availability of this fluid would add much to the dynamic study of disease. Analytical studies of the blood for metabolites, frequently evanescent in character and variable in concentration, have played a definite but limited share in this respect. The investigation of blood enzymes has followed a variable course. A few enzymes, such as the alkaline and acid phosphatases, received much attention because of their diagnostic applicability. The study of the glycolytic enzymes in cancer was given impetus by the suggestion of Warburg and Christian (1943b) that the excessive glycolytic activity of neoplasms might be manifested by the passage of various enzymes of this metabolic sequence into the blood. But, as will be pointed out more fully later, these serum enzyme activities were also found to be altered in other diseases, failed to achieve the specificity of the alkaline and acid phosphatases, and hence have had only limited applicability. On the other hand, it has been shown that in some hereditary diseases the genetic enzymic defects may be reflected in the formed elements or indeed in the serum of blood. The study of the activities of these enzymes has contributed to an understanding of the mechanisms that are involved in this group of disorders. The present paper will review our available information concerning the enzymes present in the formed elements of blood, in the plasma and serum and, where pertinent, will relate these to the corresponding enzymes in the tissues and other body fluids. It will attempt to consider the origin of these enzymes and the mechanisms regulating their concentration in the blood. It will be especially concerned with the alteration of these enzyme activities in cancer and, to some extent, in other diseases, and with the application of these alterations in diagnosis and