Kinetics and stereochemistry of hydrolysis of an N-(phenylacetyl)-?-hydroxyglycine ester catalyzed by serine ?-lactamases and DD-peptidases.

ABSTRACT: The ?-hydroxydepsipeptide 3-carboxyphenyl N-(phenylacetyl)-?-hydroxyglycinate (5) is a quite effective substrate of serine ?-lactamases and low molecular mass DD-peptidases. The class C P99 and ampC ?-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 ?-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 ?-lactamases usually prefer L(S) enantiomers and DD-peptidases D(R). Product analysis, employing peptidylglycine ?-amidating lyase, showed that the preferred enantiomer is D(R). Thus, it is the ?-lactamases that have switched preference rather than the DD-peptidases. Molecular modeling of the P99 ?-lactamase active site suggests that the ?-hydroxyl 5 of may interact with conserved Asn and Lys residues. Both ?-hydroxy and ?-amido substituents on a glycine ester substrate can therefore enhance its productive interaction with the ?-lactamase active site, although their effects are not additive; this may also be true for inhibitors.

SUBMITTER: Pelto RB 

PROVIDER: S-EPMC3684201 | biostudies-literature | 2012 Sep

REPOSITORIES: biostudies-literature