Open Accessd ‐Alanyl‐ d ‐Alanine Carboxypeptidase in the Bacterial Form and L‐Form of Proteus mirabilis
Author(s) -
MARTIN Hans Herbert,
MASKOS Christian,
BURGER Reinhard
Publication year - 1975
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1975.tb02183.x
Subject(s) - penicillin , proteus mirabilis , carboxypeptidase , chemistry , enzyme , microbiology and biotechnology , biochemistry , antibiotics , biology , escherichia coli , gene
Membranes of the bacterial form and the stable and unstable L‐forms of Proteus mirabilis contain LD and DD‐carboxypeptidase. The DD‐carboxypeptidase is inhibited non‐competitively by penicillin G. The enzyme of the bacterial form is highly penicillin‐sensitive ( K i = 4 × 10 −9 M penicillin G). Inhibition is only partly reversible by treatment with penicillinase or by dialysis against buffer. In contrast, the DD‐carboxypeptidase of the unstable L‐form, grown in the presence of penicillin, is 175‐fold less penicillin‐sensitive ( K i = 7 × 10 −7 M penicillin G). Inhibition is completely reversed by penicillinase or dialysis. After inhibition by penicillin and subsequent reactivation the penicillin sensitivity of the bacterial DD‐carboxypeptidase is similar to the sensitivity of the enzyme of the unstable L‐form. The hypothesis is proposed that P. mirabilis contains two DD‐carboxypeptidases of different penicillin sensitivity and with different mechanisms of penicillin binding. Peptidoglycan synthesis in the cell walls of the unstable L‐form is probably carried out with the help of only one DD‐carboxypeptidase, viz . the completely reactivatable enzyme with the lower penicillin sensitivity.