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The crude extracts of a novel biphenyl-degrading bacterium, Dyella ginsengisoli LA-4, can transform 2, 3-dihydroxybiphenyl, catechol and 4-chiorocatechol into the corresponding ring meta-cleavage products. And it was proved that the enzyme was a constitutive 2 ,3-dihydroxybiphenyl 1 ,2-clioxygenase. The specific activities were 7. 37, 0. 2 and 0. 06 U/mg, respectively. The effects on enzyme activities by metal ions and some inhibitors were observed. The results indicate that Fe2+ can enhance the transformation of catechol and 4-chlorocatechol, but it inhibits the transformation of 2, 3-dihydroxybiphenyl. Because the enzyme activities were completely inhibited in the presence of over 1 mmol/L H2 O2, it is determined that the enzyme is an Fe(II)-dependent extradiol dioxygenase. A conserved region of the 2, 3-dihydroxybiphenyl 1, 2-dioxygenase gene bphC was amplified by PCR, which shows 73% similarity with that of known bphC gene. [ABSTRACT FROM AUTHOR]