Breakdown of the stereospecificity of DD-peptidases and beta-lactamases with thiolester substrates.
With peptide analogues of their natural substrates (the glycopeptide units of nascent peptidoglycan), the DD-peptidases exhibit a strict preference for D-Ala-D-Xaa C-termini. Gly is tolerated as the C-terminal residue, but with a significantly decreased activity. These enzymes were also known to hydrolyse various ester and thiolester analogues of their natural substrates. Some thiolesters with a C-terminal leaving group that exhibited L stereochemistry were significantly hydrolysed by some of the enzymes, particularly the Actinomadura R39 DD-peptidase, but the strict specificity for a D residue in the penultimate position was fully retained. These esters and thiolesters also behave as substrates for beta-lactamases. In this case, thiolesters exhibiting L stereochemistry in the ultimate position could also be hydrolysed, mainly by the class-C and class-D enzymes. However, more surprisingly, the class-C Enterobacter cloacae P99 beta-lactamase also hydrolysed thiolesters containing an L residue in the penultimate position, sometimes with a higher efficiency than the D isomer.
Damblon
C
C
Laboratoire d'Enzymologie, Université de Liège, Institut de Chimie, Belgium.
Zhao
G H
GH
Jamin
M
M
Ledent
P
P
Dubus
A
A
Vanhove
M
M
Raquet
X
X
Christiaens
L
L
Frère
J M
JM
D000595:Amino Acid Sequence; D004952:Esters; D007700:Kinetics; D008969:Molecular Sequence Data; D002267:Muramoylpentapeptide Carboxypeptidase / Q000737:chemistry / Q000378:metabolism*; D013379:Substrate Specificity; D013438:Sulfhydryl Compounds; D001618:beta-Lactamases / Q000737:chemistry / Q000378:metabolism*
D004952:Esters; D013438:Sulfhydryl Compounds; D002267:Muramoylpentapeptide Carboxypeptidase; D001618:beta-Lactamases