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1knf
From Proteopedia
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Crystal Structure of 2,3-dihydroxybiphenyl 1,2-dioxygenase Complexed with 3-methyl Catechol under Anaerobic Condition
Overview
The 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.
About this Structure
1KNF is a Single protein structure of sequence from Burkholderia cepacia with FE2, MBD and TBU as ligands. Active as Biphenyl-2,3-diol 1,2-dioxygenase, with EC number 1.13.11.39 Full crystallographic information is available from OCA.
Reference
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
Page seeded by OCA on Tue Nov 20 19:24:48 2007
