{PDOC00079}
{PS00083; INTRADIOL_DIOXYGENAS}
{BEGIN}
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* Intradiol ring-cleavage dioxygenases signature *
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Dioxygenases catalyze the incorporation of both atoms of molecular oxygen into
substrates.  Cleavage of  aromatic rings is one of the most important function
of  dioxygenases.   The  substrates  of  ring-cleavage   dioxygenases  can  be
classified into two groups  according to the mode  of scission of the aromatic
ring. Intradiol enzymes  cleave the aromatic ring between two hydroxyl groups,
whereas extradiol  enzymes cleave  the aromatic  ring between  a  hydroxylated
carbon and another adjacent nonhydroxylated carbon [1]. Intradiol dioxygenases
require a nonheme  ferric ion as a cofactor.  The enzymes that  belong to this
family are:

 - Protocatechuate 3,4-dioxygenase  (EC 1.13.11.3) (3,4-PCD),  an   oligomeric
   enzyme complex  which consists of  12 copies  each  of an alpha  and a beta
   subunits. Both subunits are evolutionary related.
 - Catechol 1,2-dioxygenase (EC 1.13.11.1) (gene catA or clcA).
 - Chlorocatechol 1,2-dioxygenase (EC 1.13.11.1) (gene tfdC).

As a signature pattern for  these enzymes  we  selected a region that includes
a tyrosine residue which, in 3,4-PCD,  has been shown [2], to be implicated in
the binding of the ferric iron atom.

-Consensus pattern: [LIVMF]-x-G-x-[LIVM]-x(4)-[GS]-x(2)-[LIVMA]-x(4)-[LIVM]-
                    [DE]-[LIVMFYC]-x(6)-G-x-[FY]
                    [Y is an iron ligand]
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.

-Expert(s) to contact by email:
           Harayama S.; sharayam@ddbj.nig.ac.jp

-Last update: December 2004 / Pattern and text revised.

[ 1] Harayama S., Rekik M.
     "Bacterial aromatic ring-cleavage enzymes are classified into two
     different gene families."
     J. Biol. Chem. 264:15328-15333(1989).
     PubMed=2670937
[ 2] Ohlendorf D.H., Lipscomb J.D., Weber P.C.
     "Structure and assembly of protocatechuate 3,4-dioxygenase."
     Nature 336:403-405(1988).
     PubMed=3194022; DOI=10.1038/336403a0

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