Biosynthesis of ribose and deoxyribose in Escherichia coli.

The studies reported here are concerned with the biosynthesis of ribose and deoxyribose in Escherichia coli R-2. When these studies were undertaken the evidence available allowed no general conclusions to be drawn as to a common biosynthetic pathway for the two pentoses. Since that time numerous studies have contributed to a better understanding of the problem. Tracer studies on the origin of ribose in glucose-grown E. coli by Lanning and Cohen (1) and Bernstein (2) indicate that the sugar arises to a large extent from the oxidative decarboxylation of 6-phosphogluconate to ribulose 5-phosphate (hexose monophosphate oxidation) > Sowden et al. (3) and David and Renault (4) drew the same conclusion for ribose synthesis in Torula utilis. Bernstein (5) compared the Cl4 distribution in ribose isolated from visceral ribonucleic acid with that of liver glycogen in chicks fed C?-formate, -acetate, or -glycine. He concluded that neither the hcxose monophosphate oxidation and decarboxylation nor a pathway involving decarboxylation of a uranic acid could account for the labeling observed. Horecker and Mehler (6) have suggested that the series of reactions catalyzed by the enzymes transketolase and transaldolase (TK-TA)2 could explain the results reported by Bernstein. The origin of deoxyribose has been less certain. Racker (7) has reported the formation of deoxyribose 5-phosphate from an aldol type condensation of triose phosphate and acetaldehyde catalyzed by an enzyme from E. coZi. Shreeve and Grossman (8) on the basis of tracer studies with glycine-Cr4, considered that the deoxyribose of rat liver was formed by the aldol condensation. Lanning and Cohen (9) concluded that deoxyribose of TFr+ bacteriophage is synthesized by a 3 plus 2 carbon condensation; but they also stated that this was not the sole mechanism in E. coli growing aerobically. Evidence also has been presented for a second pathway which involves the conversion of ribose to deoxyribose at the nucleoside or nucleotide level. For example, several groups (10-12) have reported that rats convert (Y-labeled pyrimidine nucleosides to deoxyribose compounds without separation of the base and sugar. Also Amos and Magasanik (13) have reported similar results in E. coli infected with T1 bacteriophage. Recently, Grossman and