Catechol 23dioxygenase

A. calcoaceticus enzyme, molecular weight 81 000-85 000 (using different measuring techniques), is composed of two monomers and contains two mol Fe/mol. Additional substrates (poor) are 3- and 4-methylcatechol and 3-iso-propylcatechol, but a number of other catechols are not substrates. It has a broad optimum at pH 7-9, which coincides with its stability range. Its amino acid composition has been determined; methionine is the amino terminal residue [A2640].

Rhizobium leguminosarum enzyme is a homodimer, molecular weight 70 000 and optimum pH 9-9.5, which contains one mol Fe/mol [F647]. R. trifolii enzyme is also a dimer, molecular weight 107000, containing 1 mol Fe3 + /mol monomer [D672].

Candida tropicalis enzyme, optimum pH 7.6-8.0, acts on catechol, 4-methylcatechol, 3-and 4-chlorocatechol but not on other catechols [E204].

Trichosporon cutaneum enzyme has molecular weight 105 000 and 35 000 for holoenzyme and monomer respectively. Its specificity is broad, acting on catechol, 4-methylcatechol, pyrogallol and hydroxyquinol [C84].

Pseudomonas pyrocatechase II acts on catechols substituted at positions 3 and 4 with methyl, chloro or fluoro groups [B754]. P. arvilla enzyme converts pyrogallol into both a-hydroxymuconic acid and 2-pyrone-6-carboxylic acid; the latter is formed by ring closure of the ring fission product, possibly without prior release from the enzyme [B547].

Brevibacterium enzyme contains Fe3 +, apparently sulphur-bound [A1231].

Enzyme from an unspecified bacterium has an optimum between pH 7 and 10 [B525].

Catechol 2,3-dioxygenase (metapyrocatechase; E.C. 1.13.11.2)

Catechol 0 2-hydroxymuconic semialdehyde

A study carried out on extradiol dioxygenases from a series of 7 Pseudomonas strains demonstrated that each enzyme has its own quantitative specificity towards catechol, 3-

and 4-methylcatechol, 4-chlorocatechol and 2,3-dihydroxybiphenyl, ranging from good activity for most of these substrates to good activity for only 2,3-dihydroxybiphenyl [H272]. One Pseudomonas enzyme is a homotetramer, with apparent molecular weight for monomer and tetramer of 33 000 and 110000, respectively. Its optimum pH is 8-8.5 and is stable up to 70°. It acts on catechol, 3- and 4-methylcatechol; 3-fluorocatechol, and 4-chlorocatechol are poor substrates [J649]. Another study by the same research team confirmed many of these results, but gave a tetrameric molecular weight of 120 000 [G355]. P. putida enzyme is probably a homo-tetramer with subunit molecular weight 34 000 [K204].

P. arvilla enzyme oxidizes pyrogallol to a-hydroxymuconic acid [B547] and is inhibited competitively by o -nitrophenol or m -phenanthroline relative to catechol, but non-competitively relative to oxygen [A1031]. It is not inhibited by superoxide dismutase (E.C. 1.15.1.1), hence, superoxide is not the oxidizing species, nor by compounds capable of trapping singlet oxygen [A1047]. P. aeruginosa enzyme is inhibited by ATP and Mg2+ [A2832].

Bacillus thermoleovorans enzyme is a homo-tetramer, subunit molecular weight 34 700, pI 4.8, optimum pH 7.2, and contains one Fe/monomer. It is inactivated rapidly at 70° [K228].

Enzyme from a thermophilic Bacillus is inactivated by high concentrations of oxygen [J834].

Hydroxyquinol 1,2-dioxygenase (E.C. 1.13.11.37)

Burkholderia cepacia enzyme is a dimer, molecular weight 68 000. It is highly specific, forming maleylacetate [J251].

Azotobacter enzyme is a dimer, monomeric molecular weight 34 000, which is activated by Fe2+. An additional substrate is 6-chloro-1,2,4-trihydroxybenzene [H602].

Phanerochaete chrysosporium enzyme is a dimer, molecular weight 90 000. It incorporates molecular oxygen into the product. It is highly specific, but also oxidizes catechol [H284].

Was this article helpful?

0 0
Cure Your Yeast Infection For Good

Cure Your Yeast Infection For Good

The term vaginitis is one that is applied to any inflammation or infection of the vagina, and there are many different conditions that are categorized together under this ‘broad’ heading, including bacterial vaginosis, trichomoniasis and non-infectious vaginitis.

Get My Free Ebook


Post a comment