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Crystal Structure of 2,3-dihydroxybiphenyl 1,2-dioxygenase Complexed with 3-methyl Catechol under Anaerobic Condition
Structural highlights
FunctionBPHC_PARXL Shows a preference for catechols with groups immediately adjacent to the hydroxyl substituents. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe steady-state cleavage of catechols by 2,3-dihydroxybiphenyl 1, 2-dioxygenase (DHBD), the extradiol dioxygenase of the biphenyl biodegradation pathway, was investigated using a highly active, anaerobically purified preparation of enzyme. The kinetic data obtained using 2,3-dihydroxybiphenyl (DHB) fit a compulsory order ternary complex mechanism in which substrate inhibition occurs. The Km for dioxygen was 1280 +/- 70 microM, which is at least 2 orders of magnitude higher than that reported for catechol 2,3-dioxygenases. Km and Kd for DHB were 22 +/- 2 and 8 +/- 1 microM, respectively. DHBD was subject to reversible substrate inhibition and mechanism-based inactivation. In air-saturated buffer, the partition ratios of catecholic substrates substituted at C-3 were inversely related to their apparent specificity constants. Small organic molecules that stabilized DHBD most effectively also inhibited the cleavage reaction most strongly. The steady-state kinetic data and crystallographic results suggest that the stabilization and inhibition are due to specific interactions between the organic molecule and the active site of the enzyme. t-Butanol stabilized the enzyme and inhibited the cleavage of DHB in a mixed fashion, consistent with the distinct binding sites occupied by t-butanol in the crystal structures of the substrate-free form of the enzyme and the enzyme-DHB complex. In contrast, crystal structures of complexes with catechol and 3-methylcatechol revealed relationships between the binding of these smaller substrates and t-butanol that are consistent with the observed competitive inhibition. Molecular basis for the stabilization and inhibition of 2, 3-dihydroxybiphenyl 1,2-dioxygenase by t-butanol.,Vaillancourt FH, Han S, Fortin PD, Bolin JT, Eltis LD J Biol Chem. 1998 Dec 25;273(52):34887-95. PMID:9857017[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences | ||||||||||||||||||||
