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- ****************************************************
- * Glutamine amidotransferases class-II active site *
- ****************************************************
-
- 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).
-