Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:4.6.1.1 (adenylate cyclase)
 19,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Choleragen catalyzed the hydrolysis of NAD to ADP-ribose and nicotinamide; nicotinamide production was dramatically increased by L-arginine methyl ester and to a lesser extent by D- or L-arginine, but not by other basic amino acids. Guanidine was also effective. Nicotinamide formation in the presence of L-arginine methyl ester was greatest under conditions previously shown to accelerate the hydrolysis of NAD by choleragen (Moss, J., Manganiello, V. C., and Vaughan, M. (1976) Proc. Natl. Acad. Sci. U.S.A. 73, 4424-4427). After incubation of [adenine-U14C]NAD and L[3H]arginine with coleragen, a product was isolated by thin layer chromatography that contained adenine and arginine in a 1:1 ratio and has been tentatively identified as ADP-ribose-L-arginine. Parallel experiments with [carbonyl-14C]NAD have demonstrated that formation of the ADP-ribosyl-L-arginine derivative was associated with the production of [carbonyl-14C]nicotinamide. As guanidine itself was active and D- and L-arginine was equally effective in promoting nicotinamide production, whereas citrulline, which possesses a ureido rather than a guanidino function, was inactive, it seems probable that the guanidino group rather than the alpha-amino moiety participated in the linkage to ADP-ribose. Based on the assumption that the ADP-ribosylation of L-arginine by choleragen is a model for the NAD-dependent activation of adenylate cyclase by choleragen, it is proposed that the active A protomer of choleragen catalyzes the ADP-ribosylation of an arginine, or related amino acid residue in a protein, which is the cyclase itself or is critical to its activation by choleragen.
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PMID:Mechanism of action of choleragen. Evidence for ADP-ribosyltransferase activity with arginine as an acceptor. 13 9

A model system, measuring the rate of cholera-toxin-catalysed release of nicotinamide from NAD+, has been used to identify novel compounds which may serve as substrates for toxin-directed ADP-ribosylation. In a series of guanidine-containing compounds, those in which the guanidine group was connected to a large hydrophobic domain greatly stimulated the rate of toxin-catalysed nicotinamide release. The introduction of a charge centre near the guanidine group destroyed all activity. The compounds thus identified were found to inhibit the action of cholera toxin on rat liver adenylate cyclase, and this was associated with a reduction in the amount of [32P]ADP-ribosylation of a 42-kDa protein in the membranes. Guanidine-containing compounds which did not enhance toxin-catalysed release of nicotinamide from NAD+ had no effect on toxin action on adenylate cyclase, and there was a good correlation between the two activities. The results are discussed in relation to the known properties of the guanine nucleotide regulatory protein associated with adenylate cyclase systems, which is the toxin's natural substrate.
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PMID:Artificial low-molecular-mass substrates of cholera toxin. 646 87