Pathway of L-xylose and L-lyxose degradation in Aerobacter aerogenes.

Pen&e utilization in Aerobacter aerogenes has been shown from fermentation studies with Cl%beled pentoses (1, 2) and with cell extracts (3) to involve the conversion of the pentose to n-xylulose 5-phosphate, which is further metabolized via n-sedoheptulose 7-phosphate, n-fructose 6-phosphate, and intermediates of the Embden-Meyerhof pathway. Although Aerobacter aerogenes can grow on all eight of the aldopentoses,’ only Larabinose of the L-pentoses is attacked readily. The pathway for L-arabinose involves isomerization to L-ribulose (3) followed by phosphorylation at carbon 5 (4) and epimerization at carbon 4 (5) to yield n-xylulose 5-phosphate. The present report presents evidence that L-xylose and L-lyxose are isomerized to L-xylulose, which is phosphorylated and converted to the common intermediate, n-xylulose 5-phosphate, by sequential epimerization at carbons 3 and 4 (6).