Recently novel enzymes identified in the fungus Neurospora crassa and the bacterium Xanthomonas campestris were shown to phosphorolyse the D-glucopyranosyl-b-1,4-D-gluconic acid (cellobionic acid)104 liberated by cellulose lyases. These enzymes were only capable of transferring D-glucose on to the 4 position of gluconic acid (giving 172) or the 3 position of glucuronic acid (giving173), which is explained by binding of the carboxylate in the same orientation in the enzyme (Fig. 17).