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Inhibition analysis of hydroxyquinol‐cleaving dioxygenases from the chlorophenol‐degrading Azotobacter sp. GP1 and Streptomyces rochei 303
Author(s) -
Zaborina Olga,
Seitz HansJürgen,
Sidorov Igor,
Eperspächer Jürgen,
Alexeeva Elena,
Golovleva Ludmila,
Lingens Franz
Publication year - 1999
Publication title -
journal of basic microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.58
H-Index - 54
eISSN - 1521-4028
pISSN - 0233-111X
DOI - 10.1002/(sici)1521-4028(199903)39:1<61::aid-jobm61>3.0.co;2-z
Subject(s) - dioxygenase , catechol , enzyme , chemistry , stereochemistry , non competitive inhibition , substrate (aquarium) , biochemistry , streptomyces , bacteria , biology , ecology , genetics
Unlike other intradiol‐cleaving dioxygenases, hydroxyquinol 1,2‐dioxygenase (HQ‐DO) from Azotobacter sp. GP1 (for this enzyme an improved purification is described) and 6‐chlorohydroxyquinol 1,2‐dioxygenase (CHQ‐DO) from Streptomyces rochei 303 only convert 1,2,4‐trihydroxybenzene compounds and do not accept catechols as substrate. Inhibition studies revealed the ability of the two enzymes to interact with hydroxylated aromatic and chloroaromatic compounds. Thus polychlorinated catechols strongly inhibited both enzymes by fully mixed mechanism. Also for both enzymes, chlorophenols were weak or no inhibitors and methylcatechols were found to be less effective inhibitors than the corresponding chlorocatechols. Nonchlorinated hydroxylated aromatic compounds inhibited HQ‐DO but not CHQ‐DO. Mono‐ and dichlorinated hydroquinones and catechols were competitive inhibitors for HQ‐DO but they acted upon CHQ‐DO by two different mechanisms: fully competitive and fully mixed inhibition. Differences and similarities in inhibition effect and mechanism are discussed with regard to the interaction of hydroxyaromatic compounds with either enzyme. A hypothesis is presented to explain why hydroxyquinol cleaving enzymes are unable to catalyze the ring fission of catechol.