A. Lyngstadaas et al., IMPAIRED GROWTH OF AN ESCHERICHIA-COLI RPE MUTANT LACKING RIBULOSE-5-PHOSPHATE EPIMERASE ACTIVITY, Biochimica et biophysica acta (G). General subjects, 1381(3), 1998, pp. 319-330
We present evidence that ribulose-5-phosphate epimerase, a central met
abolic enzyme acting in the non-oxidative branch of the pentose-phosph
ate pathway, is encoded by a gene in the dam containing operon of Esch
erichia coli. Enzymatic assays confirm that this gene encodes ribulose
-5-phosphate epimerase activity. Disruption of the gene (rpe) causes l
oss of enzymatic activity and renders the rpe mutant unable to utilize
single pentose sugars, indicating that rpe supplies the only ribulose
-5-phosphate epimerase activity in E. coli. Growth of the rpe mutant i
s impaired in complex LB medium and severely impaired in minimal mediu
m containing glycolytic carbon sources or gluconate. Enrichment with c
asamino acids abolishes or strongly relieves growth suppression in min
imal medium. Aspartate counteracts the impaired growth in glycolytic c
arbon sources but not in gluconate. We suggest that the absence of the
Rpe enzyme causes changes in the pentose-phosphate levels which alter
the regulation of (a) metabolic enzyme(s) and thereby cause growth su
ppression and that the severity of growth suppression is related to th
e internal concentration of pentose-phosphates. Target enzymes for neg
ative regulation may be located in the early parts of the Embden-Meyer
hof-Parnas pathway and of the Entner-Doudoroff pathway and/or of carbo
hydrate transport systems feeding sugars into these sections of centra
l metabolic pathways. (C) 1998 Elsevier Science B.V. All rights reserv
ed.