title: Kinetics and stereochemistry of hydrolysis of an N-(phenylacetyl)-α-hydroxyglycine ester catalyzed by serine β-lactamases and DD-peptidases.
abstract: The α-hydroxydepsipeptide 3-carboxyphenyl N-(phenylacetyl)-α-hydroxyglycinate (5) is a quite effective substrate of serine β-lactamases and low molecular mass DD-peptidases. The class C P99 and ampC β-lactamases catalyze the hydrolysis of both enantiomers of 5, although they show a strong preference for one of them. The class A TEM-2 and class D OXA-1 β-lactamases and the Streptomyces R61 and Actinomadura R39 DD-peptidases catalyze hydrolysis of only one enantiomer of at any significant rate. Experiments show that all of the above enzymes strongly prefer the same enantiomer, a surprising result since β-lactamases usually prefer L(S) enantiomers and DD-peptidases D(R). Product analysis, employing peptidylglycine α-amidating lyase, showed that the preferred enantiomer is D(R). Thus, it is the β-lactamases that have switched preference rather than the DD-peptidases. Molecular modeling of the P99 β-lactamase active site suggests that the α-hydroxyl 5 of may interact with conserved Asn and Lys residues. Both α-hydroxy and α-amido substituents on a glycine ester substrate can therefore enhance its productive interaction with the β-lactamase active site, although their effects are not additive; this may also be true for inhibitors.
authors.affiliation: Department of Chemistry, Wesleyan University, Lawn Ave., Middletown, CT 06459, USA.
authors.forename: Ryan B
authors.initials: RB
authors.lastname: Pelto
authors.forename: R F
authors.initials: RF
authors.lastname: Pratt
mesh_terms: D000192:Actinomycetales / Q000201:enzymology; D002384:Catalysis; D020134:Catalytic Domain; D016972:Enterobacter cloacae / Q000201:enzymology; D004926:Escherichia coli / Q000201:enzymology; D005998:Glycine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D006868:Hydrolysis; D007700:Kinetics; D008958:Models, Molecular; D015394:Molecular Structure; D046929:Serine-Type D-Ala-D-Ala Carboxypeptidase / Q000378:metabolism*; D013237:Stereoisomerism; D013302:Streptomyces / Q000201:enzymology; D001618:beta-Lactamases / Q000378:metabolism*
chemical_list: D046929:Serine-Type D-Ala-D-Ala Carboxypeptidase; D001618:beta-Lactamases; D005998:Glycine