Site-directed mutagenesis studies of acetylglutamate synthase delineate the site for the arginine inhibitor

Abstract 

N-acetyl-l-glutamate synthase (NAGS), the first enzyme of bacterial/plant arginine biosynthesis and an essential activator of the urea cycle in animals, is, respectively, arginine-inhibited and activated. Site-directed mutagenesis of recombinant Pseudomonas aeruginosa NAGS (PaNAGS) delineates the arginine site in the PaNAGS acetylglutamate kinase-like domain, and, by extension, in human NAGS. Key residues for glutamate binding are identified in the acetyltransferase domain. However, the acetylglutamate kinase-like domain may modulate glutamate binding, since one mutation affecting this domain increases the K_m for glutamate. The effects on PaNAGS of two mutations found in human NAGS deficiency support the similarity of bacterial and human NAGSs despite their low sequence identity.

Abbreviations: AAK, amino acid kinase, GNAT, GCN5-related N-acetyltransferase, NAG, N-acetyl-l-glutamate, NAGK, N-acetyl-l-glutamate kinase, NAGS, N-acetyl-l-glutamate synthase, Pa, Pseudomonas aeruginosa, Ec, Escherichia coli, Ng, Neisseria gonorrhoeae, Hu, human

Keywords: N-acetyl-l-glutamate synthase, Arginine biosynthesis, Feed-back inhibition, Glutamate binding, Urea cycle errors, NAGS deficiency