Deoxyribose5-phosphate metabolism by normal liver and malignant hepatoma.

The requirement for net synthesis of deoxyribonucleic acid in a growing tissue, normal or malignant, is well established. The synthetic pathways of the purine and pyrimidine moieties of nucleic acids have been largely elucidated, but most of the available data are concerned with ribonucleic acid synthesis. The metabolic origin of the deoxyribose moiety of DNA1 is, however, not clearly established. Direct conversion in viva of cytidine to deoxycytidine without splitting of the ribosidic linkage has been observed to occur in rats (1). On the other hand, Racker (2) has described an enzymatic mechanism for the synthesis of 2-deoxy-n-ribose 5-phosphate by aldol condensation of glyceraldehyde-3-phosphate and acetaldehyde. This enzyme has been studied in detail in bacterial extracts and its occurrence in animal tissues such as mouse liver and thymus has been noted. McGeown and Malpress (3) have demonstrated the presence of the enzyme in guinea pig liver. These investigators have identified deoxyribose-5-phosphate as the product formed when either triose phosphate or fructose-l, 6-diphosphate (hexose diphosphate) were incubated with acetaldehyde and suitable enzyme preparations. Isotopic evidence that synthesis in viva of the deoxyribose moiety of DNA does occur from 2 and 3 carbon precursors has recently been described (4-6). The data presented compare the deoxyribose phosphate aldolase activity of normal tissues to that of malignant tissue and report observations on the’ fate of deoxyribose phosphate and deoxyribo-nucleosides and -nucleotides added to these tissues. A preliminary account of this work has been published (7).