Scheme 4: The two alternative pathways of aerobic degradation of phenol: o- and m- cleavage. 1, phenol monoxygenase; 2, catechol 1,2-dioxygenase; 3, muconate lactonizing enzyme; 4, muconolactone isomerase; 5, oxoadipate enol-lactone hydrolase; 6, oxoadipate succinyl- CoA transferase; 7, catechol 2,3-dioxygenase; 8, hydroxymuconic semialdehyde hydrolase; 9, 2-oxopent-4- enoic acid hydrolase; 10, 4-hydroxy-2- oxovalerate aldolase.