Open AccessMembrane‐Bound dd ‐Carboxypeptidase and ld ‐Transpeptidase of Streptococcus faecalis ATCC 9790
Author(s) -
Coyette Jacques,
Ghuysen JeanMarie,
Polacheck Itzhack,
Shockman Gerald D.,
Perkins Harold R.
Publication year - 1974
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1974.tb03504.x
Subject(s) - stereochemistry , carboxypeptidase , chemistry , residue (chemistry) , alanine , peptide , dipeptide , amino acid , hydrolysis , biochemistry , side chain , enzyme , organic chemistry , polymer
Isolated membranes of Streptococcus faecalis ATCC 9790 exhibit DD‐carboxypeptidase activity (standard reaction: Ac 2 ‐ l ‐Lys‐ d ‐Ala‐ d ‐Ala → d ‐alanine + Ac 2 ‐ l ‐Lys‐ d ‐Ala) and ld ‐trans‐peptidase activity (standard reaction: Ac 2 ‐ l ‐Lys‐ d ‐Ala + acceptor → d ‐alanine + Ac 2 ‐ l ‐Lys‐acceptor). The DD ‐carboxypeptidase activity has a considerable specificity for peptides with a C‐terminal l ‐R 3 ‐ d ‐Ala‐ d ‐Ala sequence where R 3 is an amino acid residue and a long side‐chain at the l ‐R 3 position. A corresponding DD‐transpeptidation reaction yielding the product Ac 2 ‐ l ‐Lys‐ d ‐Ala‐ d ‐[ 14 C]Ala from the system Ac 2 ‐ l ‐Lys‐ d ‐Ala‐ d ‐Ala‐f‐ d ‐[ 14 C] alanine was not detected. The ld ‐transpeptidase activity has a considerable specificity for peptide donors that have an N α ‐substituted, C‐terminal l ‐R 3 ‐ d ‐Ala sequence with a free ω‐amino group at the end of a long side‐chain at the l ‐R 3 position, and a considerable specificity for amino group acceptors that are located on a d ‐carbon in α‐position to a free carboxyl group. In the absence of acceptor, hydrolysis of the dipeptide Ac 2 ‐ l ‐Lys‐ d ‐Ala ( ld ‐carboxypeptidase activity) was not observed. Both DD ‐carboxypeptidase and ld ‐transpeptidase activities are inhibited by β‐lactam antibiotics, but their relative sensitivity differs according to the particular antibiotic used.