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* Glutamine amidotransferases class-II active site *
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A large group of biosynthetic enzymes are able to  catalyze the removal of the
ammonia group from glutamine and then to transfer this group to a substrate to
form  a new   carbon-nitrogen  group.  This catalytic  activity  is  known  as
glutamine amidotransferase (GATase) (EC 2.4.2.-) [1]. The GATase domain exists
either as a separate  polypeptidic subunit or  as part of a larger polypeptide
fused in  different  ways  to a  synthase domain.  On  the  basis  of sequence
similarities two classes of GATase domains have been identified [2,3]: class-I
(also known as trpG-type) and  class-II  (also known  as  purF-type). Class-II
GATase domains have been found in the following enzymes:

 - Amido   phosphoribosyltransferase  (glutamine   phosphoribosylpyrophosphate
   amidotransferase) (EC 2.4.2.14).  An enzyme which  catalyzes the first step
   in purine biosynthesis,  the transfer  of the ammonia group of glutamine to
   PRPP to form 5-phosphoribosylamine (gene purF in bacteria, ADE4 in yeast).
 - Glucosamine--fructose-6-phosphate  aminotransferase   (EC 2.6.1.16).   This
   enzyme catalyzes a  key reaction in amino sugar synthesis, the formation of
   glucosamine 6-phosphate from fructose 6-phosphate and glutamine  (gene glmS
   in Escherichia coli, nodM in Rhizobium, GFA1 in yeast)
 - Asparagine synthetase (glutamine-hydrolyzing) (EC 6.3.5.4).  This enzyme is
   responsible for the synthesis of asparagine from aspartate and glutamine.

A cysteine is present at the N-terminal extremity of  the  mature  form of all
these enzymes. The cysteine has been shown, in amido phosphoribosyltransferase
[4] and in  asparagine  synthetase [5] to  be  important  for   the  catalytic
mechanism.

-Consensus pattern: <x(0,11)-C-[GS]-[IV]-[LIVMFYW]-[AG]
                    [C is the active site residue]
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in SWISS-PROT: 7.

-Note: the active site cysteine is found at  the N-terminus of the MATURE form
 of all these proteins, but  in  some  cases (for example in Bacillus subtilis
 or chicken amido phosphoribosyltransferase) the enzyme is synthesized  with a
 short propeptide  which  is cleaved off post-translationally; this is why  we
 indicated the  pattern as <x(0,11)-  instead of <x(0,1)- (0 for a mature form
 without the initiator Met, 1 with the initiator Met).

-Last update: December 1992 / Text revised.

[ 1] Buchanan J.M.
     Adv. Enzymol. 39:91-183(1973).
[ 2] Weng M., Zalkin H.
     J. Bacteriol. 169:3023-3028(1987).
[ 3] Nyunoya H., Lusty C.J.
     J. Biol. Chem. 259:9790-9798(1984).
[ 4] van Heeke G., Schuster M.
     J. Biol. Chem. 264:5503-5509(1989).
[ 5] Vollmer S.J., Switzer R.L., Hermodson M.A., Bower S.G., Zalkin H.
     J. Biol. Chem. 258:10582-10585(1983).