FIG. 5.

Proposed intramolecular rearrangement mechanisms. (A) Mutases from P. pseudoalcaligenes JS45, R. eutrophus JMP134, and Mycobacterium sp. strain 4-NT, as well as the lyase from Pseudomonas strain 4-NT, convert HAB to the AP by an intramolecular transfer of the hydroxyl group. (B) The lyase from Pseudomonas strain 4-NT catalyzes an intramolecular rearrangement of 4-HABA and a second hydrolase reaction, producing protocatechuate. The mutase from P. pseudoalcaligenes converts HABA to the AP. The imine, in brackets, is proposed as an intermediate in both reactions. Solid arrows represent reactions that have been demonstrated. Dashed arrows represent the hypothetical reaction proposed in references 15 and 23.