home *** CD-ROM | disk | FTP | other *** search
- ***********************************************************
- * Aspartate and ornithine carbamoyltransferases signature *
- ***********************************************************
-
- Aspartate carbamoyltransferase (EC 2.1.3.2) (ATCase) catalyzes the conversion
- of aspartate and carbamoyl phosphate to carbamoylaspartate, the second step
- in the de novo biosynthesis of pyrimidine nucleotides [1]. In prokaryotes
- ATCase consists of two subunits: a catalytic chain (gene pyrB) and a
- regulatory chain (gene pyrI), while in eukaryotes it is a domain in a multi-
- functional enzyme (called URA2 in yeast, rudimentary in Drosophila, and CAD
- in mammals [2]) that also catalyzes other steps of the biosynthesis of
- pyrimidines.
-
- Ornithine carbamoyltransferase (EC 2.1.3.3) (OTCase) catalyzes the conversion
- of ornithine and carbamoyl phosphate to citrulline. In mammals this enzyme
- participates in the urea cycle [3] and is located in the mitochondrial
- matrix. In prokaryotes and eukaryotic microorganisms it is involved in the
- biosynthesis of arginine. In some bacterial species it is also involved in the
- degradation of arginine [4] (the arginine deaminase pathway).
-
- It has been shown [5] that these two enzymes are evolutionary related. The
- predicted secondary structure of both enzymes are similar and there are some
- regions of sequence similarities. One of these regions includes three
- residues which have been shown, by crystallographic studies [6], to be
- implicated in binding the phosphoryl group of carbamoyl phosphate. We have
- selected this region as a signature for these enzymes.
-
- -Consensus pattern: F-x-[EK]-x-S-[GT]-R-T
- [S, R, and the 2nd T bind carbamoyl phosphate]
- -Sequences known to belong to this class detected by the pattern: ALL.
- -Other sequence(s) detected in SWISS-PROT: a Streptococcus pyogenes partial
- hypothetical protein (encoded in sagP 3'region) which is, most probably, on
- the basis of sequence similarities, an OTCase.
-
- -Note: the residue in position 3 of the pattern allows to distinguish between
- an ATCase (Glu) and an OTCase (Lys).
-
- -Last update: October 1993 / Text revised.
-
- [ 1] Lerner C.G., Switzer R.L.
- J. Biol. Chem. 261:11156-11165(1986).
- [ 2] Davidson J.N., Chen K.C., Jamison R.S., Musmanno L.A., Kern C.B.
- BioEssays 15:157-164(1993).
- [ 3] Takiguchi M., Matsubasa T., Amaya Y., Mori M.
- BioEssays 10:163-166(1989).
- [ 4] Baur H., Stalon V., Falmagne P., Luethi E., Haas D.
- Eur. J. Biochem. 166:111-117(1987).
- [ 5] Houghton J.E., Bencini D.A., O'Donovan G.A., Wild J.R.
- Proc. Natl. Acad. Sci. U.S.A. 81:4864-4868(1981).
- [ 6] Ke H.-M., Honzatko R.B., Lipscomb W.N.
- Proc. Natl. Acad. Sci. U.S.A. 81:4037-4040(1984).
-