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Abstract. Of eleven substituted phenoxyacetic acids tested, only three (2,4-dichloro-, 4-chloro-2-methyl-and 2-methylphenoxyacetic acid) served as growth substrates for Alcaligenes eutroplws JMP 134. Whereas only one enzyme seems to be responsible for the initial cleavage of the ether bond, there was evidence for the presence of three different phenol hydroxylascs in this strain. 3,5-Dichlorocatechol and 5-ch loro-3-methylca techol, metabolites of the degradation of 2,4-diehlorophenoxyacetic acid and 4-cWoro-2-methylphenoxyacetic acid, respectively, were exclusively metabolized via the ortho-cleavage pathway. 2-Methylphenoxy. acetic acid-grown cells showed sim ultaneous induction of meta-and ortho-cleavage enzymes. Two catechol 1,2-dioxygcnases responsible for o rlho-cleavage of the intcr~ mediate catechols were partially purified and characterized. One of these enzymes converted 3,5-dichlorocatechol considerably faster than catechol or 3-chlorocatechoL A new enzyme for the cycloisomerisation ofmuconates was found , which exhibited high activity against the ring-cleavage products of 3,5-dichlorocatcchol and 4-chlorocatechol, but low activities against 2-chloromuconate and muconate.

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