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Link to original content: https://pubmed.ncbi.nlm.nih.gov/8663466
Required allosteric effector site for N-acetylglutamate on carbamoyl-phosphate synthetase I - PubMed Skip to main page content
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. 1996 Jul 26;271(30):18285-94.
doi: 10.1074/jbc.271.30.18285.

Required allosteric effector site for N-acetylglutamate on carbamoyl-phosphate synthetase I

C R McCudden  1 , S G Powers-Lee
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Required allosteric effector site for N-acetylglutamate on carbamoyl-phosphate synthetase I

C R McCudden et al. J Biol Chem. .
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Abstract

Carbamoyl-phosphate synthetase I (CPSase I) catalyzes the entry and rate-limiting step in the urea cycle, the pathway by which mammals detoxify ammonia. One facet of CPSase I regulation is a requirement for N-acetylglutamate (AGA), which induces an active enzyme conformation and does not participate directly in the chemical reaction. We have utilized labeling with carbodiimide-activated [14C]AGA to identify peptides 120-127, 234-237, 625-630, and 1351-1356 as potentially being near the binding site for AGA. Identification of peptide 1351-1356 confirms the previous demonstration (Rodriquez-Aparicio, L. B., Guadalajara, A. M., and Rubio, V.(1989) Biochemistry 28, 3070-3074) that the C-terminal region is involved in binding AGA. Identification of peptides 120-127 and 234-237 constitutes the first evidence that the N-terminal region of the synthetase is involved in ligand binding. Since peptides 631-638 and 1327-1348 have been identified near the ATP site of CPSase I (Potter, M. D., and Powers-Lee, S. G.(1992) J. Biol. Chem. 267, 2023-2031), the present finding of involvement of peptides 625-630 and 1351-1356 at an "allosteric" activator site was unexpected. The idea that portions of the AGA effector site might be derived from an ancestral glutamine substrate site via a gene duplication and diversification event was considered.

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