The Influence of Nucleic Acid on Dehydrogenase Systems a Contribution to the Problem of Gene Mechanism

Abstract

The cellular components comprise a vast number of different compounds, salts, proteins, carbohydrates, fats, nucleates, etc., each in a state of metabolic flux, and each interacting with others to provide the energy for specific function, the supply of structural materials, and the disposal of breakdown products. This complicated and highly diverse mechanism of the cell is regulated by a mosaic of enzyme systems which are not independent but interrelated, and which are themselves regulated and affected by extrinsic and intrinsic factors and conditions. Thus, it is possible to affect the level of particular enzymes by nutritive deprivation of the cell, by the application of chemical inhibitors or stimulators, and by cellular mutations whether spontaneous or induced. Any attempt to elucidate these phenomena in toto is quite obviously a formidable task. The biochemist at present can study only a few systems at a time, under conditions often considerably removed from the physiological, and, as yet, with tools and concepts alike available only for first approximations. Biological chemistry owes its beginnings to the insight of men like Miescher, Kossel, and others, who believed that problems in tissue function might be at least partially explicable in terms of the chemical properties of isolated components and systems. It is with this hope undimmed, and with due recognition of the limitations inherent in the approach, that an attempt at a study of a chemical basis of gene action may be begun (Greenstein and Chalkley, '45). Nucleic acid combined with specific proteins appears to yield conjugated compounds often with remarkable biological properties. Among these compounds are the viruses and the components of the chromosomes. Considerable information exists suggestive of a linking of nucleic acids with gene mechanisms, but in the absence of evidence for the isolated gene any attempt to identify the latter as a nucleoprotein must be treated with some reserve. Nevertheless, there is evidence that growth and reduplication are associated with the presence of nucleic acid, and the relation of the latter type of substance with the gene may thus be strongly inferred. Since the genic material exerts a controlling influence over the multitudinous functional processes of the cell, it may be assumed that it accomplishes this not by a remote form of control but by specific kinds of chemical interaction with the cellular components involved in individual reactions, i. e., enzymes (cf. Tatum and Beadle, '45). It is for this reason that the study of the chemical interaction of nucleic acid with various kinds of cellular components should yield sig-