TY - JOUR
T1 - 18O studies of pyrogallol cleavage by catechol 1,2-dioxygenase
AU - Mayer, R. J.
AU - Que, L.
N1 - Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.
PY - 1984
Y1 - 1984
N2 - 18O labeling studies on the catechol 1,2-dioxygenase-catalyzed oxidative cleavage of pyrogallol demonstrate that the enzyme functions both as a dioxygenase and a monooxygenase in this reaction. Two products are observed, 2-pyrone-6-carboxylic acid, 99% singly labeled at the carboxylate, and 2-hydroxy-cis,cis-muconic acid, 74% doubly labeled (one 18O at each carboxylate) and 24% single labeled (one 18O at either carboxylate). The labeling pattern observed shows that 2-pyrone-6-carboxylic acid cannot be derived enzymatically from the lactonization of the 2-hydroxy-cis,cis-muconic acid, thus eliminating the dioxetane as an intermediate in the dioxygenase mechanism. The observations are interpreted to indicate the intermediacy of 2-hydroxymuconic anhydride. This anhydride or the corresponding muconyl enzyme species must be sufficiently long-lived to allow the exchange of labeled hydroxide with solvent. Evidence for mechanism-based enzyme inactivation by a pyrogallol-derived intermediate is also presented.
AB - 18O labeling studies on the catechol 1,2-dioxygenase-catalyzed oxidative cleavage of pyrogallol demonstrate that the enzyme functions both as a dioxygenase and a monooxygenase in this reaction. Two products are observed, 2-pyrone-6-carboxylic acid, 99% singly labeled at the carboxylate, and 2-hydroxy-cis,cis-muconic acid, 74% doubly labeled (one 18O at each carboxylate) and 24% single labeled (one 18O at either carboxylate). The labeling pattern observed shows that 2-pyrone-6-carboxylic acid cannot be derived enzymatically from the lactonization of the 2-hydroxy-cis,cis-muconic acid, thus eliminating the dioxetane as an intermediate in the dioxygenase mechanism. The observations are interpreted to indicate the intermediacy of 2-hydroxymuconic anhydride. This anhydride or the corresponding muconyl enzyme species must be sufficiently long-lived to allow the exchange of labeled hydroxide with solvent. Evidence for mechanism-based enzyme inactivation by a pyrogallol-derived intermediate is also presented.
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M3 - Article
C2 - 6490644
AN - SCOPUS:0021645767
SN - 0021-9258
VL - 259
SP - 13056
EP - 13060
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 21
ER -