Molecular basis for the substrate selectivity of bicyclic and monocyclic extradiol dioxygenases.

Extradiol dioxygenases play a key role in determining the specificities of the microbial aromatic catabolic pathways in which they occur. To identify the structural determinants of specificity in this class of enzymes, variants of 2,3-dihydroxybiphenyl (DHB) 1,2-dioxygenase (DHBD) were investigated. Structural data of the DHBD/DHB complex informed the design of seven variants at four positions: V148W, V148L, M175W, A200I, A200W, P280W, and V148L/A200I.

Characterization of extradiol dioxygenases from a polychlorinated biphenyl-degrading strain that possess higher specificities for chlorinated metabolites.

Recent studies demonstrated that 2,3-dihydroxybiphenyl 1,2-dioxygenase from Burkholderia sp. strain LB400 (DHBDLB400; EC 1.13.

Identification and analysis of a bottleneck in PCB biodegradation.

The microbial degradation of polychlorinated biphenyls (PCBs) provides the potential to destroy these widespread, toxic and persistent environmental pollutants. For example, the four-step upper bph pathway transforms some of the more than 100 different PCBs found in commercial mixtures and is being engineered for more effective PCB degradation. In the critical third step of this pathway, 2,3-dihydroxybiphenyl (DHB) 1,2-dioxygenase (DHBD; EC 1.

The mechanism-based inactivation of 2,3-dihydroxybiphenyl 1,2-dioxygenase by catecholic substrates.

2,3-Dihydroxybiphenyl 1,2-dioxygenase (EC ), the extradiol dioxygenase of the biphenyl biodegradation pathway, is subject to inactivation during the steady-state cleavage of catechols. Detailed analysis revealed that this inactivation was similar to the O(2)-dependent inactivation of the enzyme in the absence of catecholic substrate, resulting in oxidation of the active site Fe(II) to Fe(III). Interestingly, the catecholic substrate not only increased the reactivity of the enzyme with O(2) to promote ring cleavage but also increased the rate of O(2)-dependent inactivation.