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DIOKSYGENAZY - KLUCZOWE ENZYMY
ROZKŁADU ZWIĄZKÓW AROMATYCZNYCH
PRZEZ DROBNOUSTROJE
Danuta Wojcieszyńska, Izabela Greń, Sylwia Łabużek
Uniwersytet Śląski, Wydział Biologii i Ochrony Środowiska, Katedra Biochemii
ul. Jagiellońska 28, 40-032 Katowice, tel. (32) 2009 576, fax 032 2009 361,
e-mail: dmanka@us.edu.pl
Wpłynęło w grudniu 2003
1. Wprowadzenie. 2. Charakterystyka dioksygenaz hydroksylujących. 3. Budowa i właściwości biochemiczne dioksygenaz
intradiolowych. 4. Budowa i właściwości biochemiczne dioksygenaz
ekstradiolowych. 5. Toksyczność intermediatów meta-rozszczepienia
Dioxygenases-key enzymes for degradation of aromatic compounds by microorganisms
Abstract: Oxygen-activating enzymes with mononuclear non-heme active participate in many important metabolic pathways of the environmental significance. The ring dihydroxylation is non-specific preliminary step in the catabolic pathway and plays an important role in the activation of resonance-stabilized aromatic compounds before the subsequent catabolism. Dihydroxylate intermediates such as catechol, hydroxyquinol or protocatechuate are cleavaged between their two hydroxyl groups
(ortho cleavage) by catechol 1,2-dioxygenase, hydroxyquinol 1,2-dioxygenase or protocatechuate 3,4-dioxygenase. The iron atom in the pentacoordinate active centre of these enzymes remains in the high-spin Fe (III) state during
catalysis. Extradiol dioxygenases catalyze the ring-cleavage at the C-C bond adjacent to the vicinal hydroxyl groups. These dioxygenases typically contain non-heme iron Fe (II) in their active site but have been also shown to be active with Mn (II). The catechol 2,3-dioxygenase catalytic cycle is supposed to comprise a complexion of iron ion by monoanionic catecholate as a bidentate ligand. The ring cleavage reaction is proposed to proceed via an attack of the iron-bound activated oxygen on the nonhydroxylated position vicinal to the carbon atom bearing the phenolate anion. When extradiol dioxygenases cleave 3-chlorocatechol, they usually become inactivated. This inactivation might be caused by the strong chelating activity of 3-chlorocatechol or by suicide inactivation of the enzyme due to the formation of reactive
intermediate.
1. Introduction. 2. Characterization of hydroxylating
dioxygenases. 3. Structure and biochemical properties of intradiol
dioxygenases. 4. Structure and biochemical properties of extradiol
dioxygenases. 5. Toxic intermediates of meta-cleavage
Słowa kluczowe: dioksygenazy intra- i ekstradiolowe,
meta-rozszczepienia
Key words: intra- and extradiol dioxygenases, meta-cleavage |
