Growth of Aerobacter aerogenes on D-arabinose: origin of the enzyme activities

Mutants of Aerobacter aerogenes can be selected which are capable of utilizing d-arabinose as a sole source of carbon and energy for growth. Mutants can also be selected which are capable of using l-xylose. The mutational event permitting the utilization of d-arabinose results in the constitutive synthesis of certain enzymes of the l-fucose catabolic pathway. l-Fucose isomerase catalyzes the first reaction in the degradation of d-arabinose: the isomerization of d-arabinose to d-ribulose. No other type of mutation appears to be required to initiate growth on d-arabinose, and wild-type cells induced for the enzymes of the l-fucose catabolic pathway are capable of growth on d-arabinose. The first reaction in the catabolism of l-xylose, the isomerization of l-xylose to l-xylulose, also appears to be catalyzed by constitutively synthesized l-fucose isomerase.