Labeling of glucose, ribose, and deoxyribose by 1- and 2-C14-glycine in regenerating rat liver.

The present study was intended to provide information on the carbon sources of deoxyribose in animal tissues. Some tracer studies (2-5) have indicated that ribose of certain nucleosides or nucleotides is converted to deoxyribose without rupture of the nucleosidic linkage. However, evidence from cell-free preparations of animal tissues (6, 7) as well as microorganisms (6) has suggested an origin of deoxyribose separate from that of ribose and involving a condensation of a 2-carbon unit (acetaldehyde) with a 3-carbon unit (glyceraldehyde 3-phosphate). Different origins for the two pentoses in regenerating rat liver were also suggested by the finding that, whereas the two pentoses were labeled to an equal extent when formed from 1-Cleacetate, ribose was labeled 5 times as much as deoxyribose when formed from 2Cleacetate (8). Furthermore, NaHCW3, which labels essentially only carbon-3 of ribose in rat liver, has been found to place into carbon-l two-thirds as much Cl4 as into carbon-3 of deoxyribose (9). In the present study Ci4-labeled glycine was used to compare the molecular pattern of labeling in various sugars from regenerating rat liver in order to test, among other possibilities, the supposition that deoxyribose might be formed from the porphyrin precursor, &aminolevulinic acid, or a compound similar in structure and origin.