FIG. 5.
Working model for the influence of a yjgF mutation on purF-independent PRA synthesis. The features of this model are described in the text (see Discussion). Depicted is a generic enzyme in central metabolism that has a 2o reaction generating metabolite X. The two distinct TrpDE-dependent PRA-forming reactions supported by the data herein are depicted and labeled 1 and 2. Activity 1 is shown to generate PRA from substrate X that is normally sequestered and/or eliminated by YjgF. Activity 2 has been described previously (36) and is considered to be a weak activity that can be enhanced by overexpression or mutation.