title: Identification and purification of distinct isomerase and decarboxylase enzymes involved in the 4-hydroxyphenylacetate catabolic pathway of Escherichia coli.
abstract: The possible involvement of an isomerase in the 4-hydroxyphenylacetate meta-cleavage pathway has been studied. 5-Carboxymethyl-2-hydroxymuconate has been shown to undergo both spontaneous and enzyme-catalysed isomerisation to give 5-carboxymethyl-2-oxo-hex-3-ene-1,5-dioate, a compound with an absorbance maximum at 246 nm. The latter compound rather than the former is the substrate for a decarboxylase that produces 2-hydroxyhepta-2,4-diene,1,7-dioate. The isomerase and decarboxylase enzymes have been purified to over 90% homogeneity. Mg2+ is required for the decarboxylase reaction but not for the isomerase.
mesh_terms: D019748:Carbon-Carbon Double Bond Isomerases; D002262:Carboxy-Lyases / Q000302:isolation & purification / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology*; D007535:Isomerases / Q000302:isolation & purification / Q000378:metabolism*; D010648:Phenylacetates / Q000378:metabolism*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D010648:Phenylacetates; C026246:4-hydroxyphenylacetate; D002262:Carboxy-Lyases; C031940:5-oxopent-3-ene-1,2,5-tricarboxylate decarboxylase; D007535:Isomerases; D019748:Carbon-Carbon Double Bond Isomerases; C031939:5-carboxymethyl-2-hydroxymuconate delta-isomerase