Role of the yiaR and yiaS Genes of Escherichia coli in Metabolism of Endogenously Formed l-Xylulose

Genes yiaP and yiaR of the yiaKLMNOPQRS cluster of Escherichia coli are required for the metabolism of the endogenously formed l-xylulose, whereas yiaS is required for this metabolism only in araD mutants. Like AraD, YiaS was shown to have l-ribulose-5-phosphate 4-epimerase activity. Similarity of YiaR to several 3-epimerases suggested that this protein could catalyze the conversion of l-xylulose-5-phosphate into l-ribulose-5-phosphate, thus completing the pathway between l-xylulose and the general metabolism.