PA5260 Pre-uroporphyrinogen synthase MSSREIRIATRQSALALWQAEYVKARLEQAHPGLTVTLLPMTSRGDKLLDAPLAKIGGKGLFVKELETALLEGAADIAVHSMKDVPMDFPEGLGLYTICEREDPRDAFVSNTYASLEQLPAGSVVGTSSLRRQAQLLARRPDLQIRFLRGNVNTRLAKLDAGEYDAIILAAAGLIRLGFESRIRSSISVDDSLPAGGQGAVGIECRTADSDLHALLEPLHHTDTALRVTAERALNKRLNGGCQVPIACYAIREGDQLWLRGLVGQPDGTQLLRAEGRAPLAEAEALGVRVAEDLLEQGAEAILEAVYGEAGHP 313 hemC Porphobilinogen deaminase HEM3_PSEAE Hydroxymethylbilane synthase Tetrapolymerization of the monopyrrole PBG into the hydroxymethylbilane pre-uroporphyrinogen in several discrete steps.