Ferrous protocatechuate 3,4-dioxygenase

This enzyme is colorless and contains the ferrous form of iron as the sole cofactor53,54 3,4-Dihydroxyphenylacetate 2,3-dioxygenase catalyzes the reaction shown in Eq. (14) and is an example of the proximal extradiol cleavage89-91. Protocatechuate 4,5-dioxygenase catalyzes the reaction shown in Eq.(15) and is an example of the distal extradiol cleavage92-94. ... 

As shown in Table 3 an almost homogeneous preparation of protocatechuate 4,5-dioxygenase purified from a Pseudomonas sp. grown with protocatechuic acid as the major carbon source has a specific activity of 160 /imoles/min/mg of protein with a molecular weight of approximately 150,000. One g-atom of ferrous iron is present per mole of enzyme94. The enzyme has also been purified from extracts of p-hydroxybenzoate-induced Pseudomonas testeronil2S The enzyme has a molecular weight of about 140,000 with a specific activity of about 12. 

Co-factor studies have been performed for all the enzymes listed, except for dihydroxy benzoate extradiol dioxygenase. Tests for dependence on ferrous ions and reducing agents and of inhibition by ferrous chelators and oxidizing agents indicate the presence of iron in the ferrous state in the active forms of metapyrocatechase 116), protocatechuate 83,117), dihydroxykynurenate (2), homoprotocatechuate 118), carboxy-... 

---