- Structure of porphobilinogen synthase from Pseudomonas aeruginosa in complex with 5-fluorolevulinic acid suggests a double Schiff base mechanism. Frère, F., Schubert, W.D., Stauffer, F., Frankenberg, N., Neier, R., Jahn, D., Heinz, D.W. J. Mol. Biol. (2002)