Beijing Normal/31 July 2008

Today we discussed about the bottleneck step in the PCBs degradation pathway.

DHBD(2,3-dihydroxybiphenyl 1,2-dioxygenase), the third enzyme of the bph pathway, is of particular significance because it is incapable o f catalyzing the ring cleavage step and is subject to various types of inhabitation, as well as suicide inactivation. According to the recent research, ortho-chlorinated PCB metabolites (DHBs) are potent and physiologically significant inhibitors of DHBD, so we design a feedback activation pathway to increase the BphC transcription and expression under a 2, 3-DHBP and 4-CB inducible promoter Ppcb. As 2, 3-DHBP is the second metabolite in the pathway, 2, 3-DHBP at a concentration more than 0.1mM will induce the activate Ppcb and thus increase gene expression downstream.