Aromatic metabolism in Rhizobium trifolii - protocatechuate 3,4-dioxygenase
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Protocatechuate 3,4-dioxygenase (EC 18.104.22.168) has been purified 42-fold from 4-hydroxybenzoate-grown cells of Rhizobium trifolii TA1, where it constitutes about 2% of the cell protein. The dioxygenase has a molecular weight of 220,000, with two dissimilar sub-units of molecular weights 29,000 and 26,500, corresponding to an α4β4 composition. The enzyme is specific for protocatechuate, with a Km of 1.75×10-5 M and maximum activity at pH 9.2. Metal removal and replacement studies indicate that the enzyme contains complexed Fe3+ which is required for activity. Direct atomic absorption analysis gave 1.3–1.5 g atoms Fe3+ per mole of isolated enzyme, but correction for metal-deficient proteins suggests that the value is close to 2.
|Publication Type:||Journal Article|
|Murdoch Affiliation:||School of Environmental and Life Sciences|
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