BIOSYNTHESIS OF PENTOSE IN ESCHERICHIA COLI

Abstract

The biosynthesis of ribose and deoxyribose in Escherichia coli involves both the oxidative pathway through 6-phosphogluconate and the nonoxidative pathway through the transketolase and transaldolase sequence (Lanning and Cohen, 1954; Bernstein, 1956; Bagatell, Wright, and Sable, 1959). The proportions of the oxidative and nonoxidative pathways depend on the nature of the principal carbon source in the medium, on the stage of growth of the culture, and on the previous history of the culture (Szynkiewicz, Sable, and Pflueger, 1961). In addition evidence has been presented that ribose and deoxyribose have a common origin in this organism (Bernstein and Sweet, 1958; Bagatell et al., 1959). Two studies (Lanning and Cohen, 1955; Loeb and Cohen, 1959) suggest that in bacteriophage-infected E. coli the nonoxidative pathway becomes of greater importance. The studies reported here support the view that both pathways are of considerable importance in the biosynthesis of deoxyribose in the presence of bacteriophage infection. Racker (1952) found an aldolase in E. coli that catalyzes the reversible reaction: CH2OPO3H2-CHOH-CHO + CH3-CHO = CH2OPO3H2-CHOH-CHOH-CH2-CHO and it has been considered that this reaction or a similar type of aldol condensation of 3-carbon and 2-carbon precursors might be an important mechanism in the biosynthesis of deoxyribose. Evidence is presented here that the biosynthesis does not occur by such an aldol condensation. MATERIALS AND METHODS E. coli strain R-2 and bacteriophage strain T2H were maintained and cultured as described

Biosynthesis of deoxyribose in wheat embryos

“…Glucose-6-1 'C Feeding Experiments. Of the four possible metabolic pathways of deoxyribose biosynthesis previously discussed, the condensation of acetaldehyde and glyceraldehyde 3-phosphate by the enzyme deoxyribose phosphate aldolase has received little support in that the enzyme affinity for acetaldehyde is too low to form any significant amount of product in vivo (Wright et al, 1961;Fossitt and Bernstein, 1963; Ghosh and Bernstein, 1963;Hammersten et al, 1950). The glucuronic acid-xylulose cycle appears to be relatively unimportant for the biosynthesis of deoxyribose and ribose, at least in animals (Hiatt and Lareau, 1958).…”

AS‐1 cyanophage infection inhibits the photosynthetic electron flow of photosystem II in Synechococcus sp. PCC 6301, a cyanobacterium

“…Synechococcus sp. cells (3)(4)(5) x 10' cells ml-') were grown in Allen medium and infected by cyanophage AS-l [6] at multiplicity of infection of 5-10 at 39°C as described [lo]. Growth of the cultures was monitored either spectrophotometrically at 800 nm or by measurement of their chlorophyll-a content as described earlier [11,12].…”

BIOSYNTHESIS OF RIBOSE AND DEOXYRIBOSE IN PSEUDOMONAS SACCHAROPHILA

“…The observed differences in isotopic patterns may indicate the presence of an alternate pathway for the biosynthesis of deoxyribose in P. saccharophila. It is also possible that these differences may be a function of compartmentation of precursor pools or other environmental influences (Wright, Sable, and Baily, 1961). Ghosh and Bernstein (1963) showed that NaHC1403 given to young adult rats results in drastically different patterns of C'4 in the ribose and deoxyribose of the nucleic acids isolated from the liver.…”