3-DIMENSIONAL STRUCTURE OF 2,3-DIHYDROXYBIPHENYL DIOXYGENASE (BPHC ENZYME) FROM PSEUDOMONAS SP STRAIN-KKS102 HAVING POLYCHLORINATED BIPHENYL (PCB)-DEGRADING ACTIVITY

The three-dimensional structure of an enzyme, 2,3-dihydroxybiphenyl di oxygenase, from Pseudomonas sp. strain KKS102 has been solved by X-ray crystal structure analysis. The enzyme conventionally called ''BphC'' is an important member in the biodegradation pathway for PCBs (polych lorinated biphenyls) which are the widely distributed environmental po llutants. The BphC enzyme is an oligomeric enzyme made up of eight ide ntical subunits of 292 amino acid residues. Each subunit consists of t wo domains: Domain 1 (residues 1 to 135) and Domain 2 (resiudes 136 to 292). Each domain consists of two repetitions of a unique folding mot if each consisting of ca. 55 amino acid residues. The unique motif may be classified into an alpha-beta sandwich structure having a ''beta a lpha beta beta beta'' type topology. In the active site of each subuni t, one Fe ion surrounded by five ligands roughly arranged in a trigona l bipyramidal geometry was found.