Pentose Fermentation by Lactobacillus Plantarum

Extracts of Lactobucillus plantarum derived from cells grown on Larabinose contain an active isomerase, which converts L-arabinose to Lribulose (1, 2), and a ribulokinase, which catalyzes the formation of L-ribulose &phosphate (3,4). Such extracts also catalyze the conversion of L-ribulose 5-phosphate to D-xylulose 5-phosphate, which has been shown to be the key intermediate in pentose fermentation by L. plantarum (5, 6). On the basis of known enzymatic reactions, the accompanying pathway can now be written for the fermentation of L-arabinose in this organism. The conversion of L-ribulose 5-phosphate to n-xylulose 5-phosphate was first demonstrated by Wolin, Simpson, and Wood (7), with an enzyme isolated from extracts of Aerobacter aerogenes. Since the reaction catalyzed by this enzyme is similar to that catalyzed by UDPG’ 4-epimerase (8), the enzyme will be named L-ribulose-5-phosphate 4-epimerase.2 The enzyme has now been obtained in highly purified form from L. plantarum. Its properties and possible cofactor requirements will be considered.