Earticle

초록

영어

The aerobic degradation enzyme system of biphenyl has been characterized well in a variety of bacteria. It is involved in the degradation of polychlorinated biphenyls (PCBs), which have caused environmental problems by their long-lasting environmental contamination. At the initial step of this system biphenyl is hydroxylated by a biphenyl dioxygenase to generate a dihydrodiol intermediate, which is converted to a diol intermediate, 2,3-dihydroxybiphenyl by a dehydrogenase. The aromatic ring of 2,3-dihydroxybiphenyl is cleaved by an extradiol ring-cleavage dioxygenase to form a phenylhexadienoate, whose side chain is trimmed by a hydrolase to produce a pentadienoate and a benzoate. Pentadienoate is metabolized by the actions of a hydratase and an aldolase via oxovalerate to pyruvate and acetoaldehyde, which is converted to acetyl-CoA by acetoaldehyde dehydrogenase. Benzoate is metabolized through the independent benzoate pathway via a dihydroxybenzoate, catechol and 3-oxoadipate to succinate and acetyl-CoA. Pyruvate, succinate and acetyl-CoA formed from biphenyl are utilized in TCA cycle. PCBs are co-metabolized by this biphenyl degradation system. In gram-negative biphenyl-degrading bacteria the upper and lower catabolic pathway enzyme genes responsible for the enzyme steps from biphenyl to benzoate and pentadienoate and those from pentadienoate to acetyl-CoA, respectively, are coded in a single gene cluster. On the other hand, the upper and lower pathway enzymes of biphenyl catabolism are coded by at least five separate gene clusters and multiple isozymes are responsible for each enzyme step in the gram-positive biphenyl-degrading bacterium, Rhodococcus jostii RHA1. In addition a couple of regulatory systems are simultaneously involved in the induction of these catabolic pathway enzyme genes in RHA1. The strain RHA1 grows on a variety of aromatics such as benzene and alkylbenzenes. The multiple enzyme and regulatory systems are appeared to be responsible for the growth on and degradation of a variety of aromatics in RHA1. The advantages and disadvantages of multiple enzyme systems will be discussed.

저자

• Masao Fukuda [ Department of Bioengineering, Nagaoka University of Technology Kamitomioka 1603-1, Nagaoka, Niigata 940-2188, Japan ]

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간행물

표지보기 관심저널 등록

• 간행물명

  한국생물공학회 학술대회

• 간기

  반년간

• 수록기간

  1985~2013

• 십진분류

  KDC 476 DDC 576