Specificity ofaCatabolic Pathway-a Lesson Learned fromIndirect Assays

Studies withpurified orcinol hydroxylase suggest that, contrary toprevious conclusions, theenzymesoftheorcinol pathway cannottransform analogous compounds tocommon metabolites. Thesubstrate analogues oforcinol uncouple electronflowfromreduced nicquinamide adenine dinucleotide tooxygenfromthehydroxylation reaction catalyzed byorcinol hydroxylase. We haveshownthatorcinol iscatabolized by Pseudomonas putida 01bya sequenceofreactionsinvolving hydroxylation to yield 2,3,5trihydroxytoluene followed bymeta-cleavage to give2,4,6-trioxoheptanoate; subsequent hydrolysis ofthis product gives acetate andpyruvate (7; D.W.Ribbons andY.Ohta,Bacteriol. Proc., p. 9,1970). CH3 CH3 CH3 ,OH ~~~~~ACETATE