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* Prokaryotic-type carbonic anhydrases signatures *
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Carbonic anhydrases (EC 4.2.1.1) (CA) are zinc  metalloenzymes  which catalyze
the reversible hydration of carbon dioxide.

In Escherichia  coli,  CA  (gene cynT) is involved in recycling carbon dioxide
formed in the bicarbonate-dependent decomposition  of cyanate by cyanase (gene
cynS). By this action, it  prevents the depletion of cellular bicarbonate [1].
In photosynthetic bacteria and plant chloroplast, CA is essential to inorganic
carbon fixation [2].

Prokaryotic and plant chloroplast CA are structurally and evolutionary related
and form  a family distinct from the one which groups the many different forms
of eukaryotic CA's.

The hypothetical Escherichia coli protein yadF also belongs to this family.

We developed two signature patterns for this family of enzymes.  Both patterns
contain conserved  residues  that  could be involved in binding zinc (cysteine
and histidine).

-Consensus pattern: C-S-D-S-R-[LIVM]-x-[AP]
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in SWISS-PROT: NONE.

-Consensus pattern: [EQ]-Y-A-[LIVM]-x(2)-[LIVM]-x(4)-[LIVM](3)-x-G-H-x(2)-C-G
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in SWISS-PROT: NONE.

-Last update: June 1994 / Patterns and text revised.

[ 1] Guilloton M.B., Korte J.J., Lamblin A.F., Fuchs J.A., Anderson P.M.
     J. Biol. Chem. 267:3731-3734(1992).
[ 2] Fukuzawa H., Suzuki E., Komukai Y., Miyachi S.
     Proc. Natl. Acad. Sci. U.S.A. 89:4437-4441(1992).