FIG. 3.

Compartmentation of quinate catabolism in Acinetobacter. Mutations blocking both pcaK and vanK impede growth with quinate, and cells containing these mutations accumulate protocatechuate in the growth medium. Thus, in accord with earlier suggestions, the initial steps in quinate utilization appear to take place on the outer surface of the inner cell membrane. Not shown in the figure is shikimate which is catabolized directly to dehydroshikimate by QuiA. Compartmentation keeps catabolic enzymes that act upon shikimate and dehydroshikimate physically separate from enzymes that must supply these compounds as biosynthetic intermediates under all growth conditions.