Biomaterial Database

Inactivation of the thiol RTEM-1 beta-lactamase by 6-beta-bromopenicillanic acid. Identity of the primary active-site nucleophile. 1987

A K Knap, and R F Pratt

Department of Chemistry, Wesleyan University, Middletown, CT 06457.

The thiol RTEM-1 beta-lactamase [Sigal, Harwood & Arentzen (1982) Proc. Natl. Acad. Sci. U.S.A. 79, 7157-7160] is inactivated by 6-beta-bromopenicillanic acid with formation of a characteristic chromophore, absorbing maximally at 350 nm, which is covalently bound to the enzyme. Model studies suggest that the chromophore is that of a 6-carboxylate thiol ester of 2,3-dihydro-2,2-dimethyl-1,4-thiazine-3,6-dicarboxylate, which can arise by rearrangement of the thiol-penicilloate obtained by thiolysis of the beta-lactam of 6-beta-bromopenicillanate. Loss of activity of the enzyme is also concerted with disappearance of its single (cysteine) thiol group. These results indicate that the thiol group of this enzyme is indeed a nucleophilic catalyst in beta-lactam turnover. The thiol beta-lactamase is also inactivated by clavulanic acid with formation of a chromophore, presumably a 3-aminoacrylate thiol ester, at 308 nm. Both 6-beta-bromopenicillanate and clavulanate are hydrolysed more slowly by the thiol enzyme than by the native serine beta-lactamase, but, probably as a consequence of this, both compounds inactivate the former enzyme more efficiently. Cefoxitin, a poor substrate of the native enzyme, does not appear to interact covalently with the thiol beta-lactamase.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D010397	Penicillanic Acid	A building block of penicillin, devoid of significant antibacterial activity. (From Merck Index, 11th ed)	Acid, Penicillanic
D002621	Chemistry	A basic science concerned with the composition, structure, and properties of matter; and the reactions that occur between substances and the associated energy exchange.
D002969	Clavulanic Acids	Acids, salts, and derivatives of clavulanic acid (C8H9O5N). They consist of those beta-lactam compounds that differ from penicillin in having the sulfur of the thiazolidine ring replaced by an oxygen. They have limited antibacterial action, but block bacterial beta-lactamase irreversibly, so that similar antibiotics are not broken down by the bacterial enzymes and therefore can exert their antibacterial effects.	Acids, Clavulanic
D001618	beta-Lactamases	Enzymes found in many bacteria which catalyze the hydrolysis of the amide bond in the beta-lactam ring. Well known antibiotics destroyed by these enzymes are penicillins and cephalosporins.	beta-Lactamase,beta Lactamase,beta Lactamases
D001665	Binding Sites	The parts of a macromolecule that directly participate in its specific combination with another molecule.	Combining Site,Binding Site,Combining Sites,Site, Binding,Site, Combining,Sites, Binding,Sites, Combining
D013053	Spectrophotometry	The art or process of comparing photometrically the relative intensities of the light in different parts of the spectrum.
D055598	Chemical Phenomena	The composition, structure, conformation, and properties of atoms and molecules, and their reaction and interaction processes.	Chemical Concepts,Chemical Processes,Physical Chemistry Concepts,Physical Chemistry Processes,Physicochemical Concepts,Physicochemical Phenomena,Physicochemical Processes,Chemical Phenomenon,Chemical Process,Physical Chemistry Phenomena,Physical Chemistry Process,Physicochemical Phenomenon,Physicochemical Process,Chemical Concept,Chemistry Process, Physical,Chemistry Processes, Physical,Concept, Chemical,Concept, Physical Chemistry,Concept, Physicochemical,Concepts, Chemical,Concepts, Physical Chemistry,Concepts, Physicochemical,Phenomena, Chemical,Phenomena, Physical Chemistry,Phenomena, Physicochemical,Phenomenon, Chemical,Phenomenon, Physicochemical,Physical Chemistry Concept,Physicochemical Concept,Process, Chemical,Process, Physical Chemistry,Process, Physicochemical,Processes, Chemical,Processes, Physical Chemistry,Processes, Physicochemical
D019818	Clavulanic Acid	A beta-lactam antibiotic produced by the actinobacterium Streptomyces clavuligerus. It is a suicide inhibitor of bacterial beta-lactamase enzymes. Administered alone, it has only weak antibacterial activity against most organisms, but given in combination with other beta-lactam antibiotics it prevents antibiotic inactivation by microbial lactamase.	Clavulanate,BRL-14151,Clavulanate Potassium,Clavulanic Acid, Monopotassium Salt,Clavulanic Acid, Monosodium Salt,MM-14151,Potassium Clavulanate,Sodium Clavulanate,BRL 14151,BRL14151,Clavulanate, Potassium,Clavulanate, Sodium,MM 14151,MM14151,Potassium, Clavulanate
D065093	beta-Lactamase Inhibitors	Endogenous substances and drugs that inhibit or block the activity of BETA-LACTAMASES.	beta Lactamase Inhibitor,beta Lactamase Inhibitors,beta-Lactamase Inhibitor,beta Lactamase Antagonists,Antagonists, beta Lactamase,Inhibitor, beta Lactamase,Inhibitor, beta-Lactamase,Inhibitors, beta Lactamase,Inhibitors, beta-Lactamase,Lactamase Antagonists, beta,Lactamase Inhibitor, beta,Lactamase Inhibitors, beta