From growth to autolysis: the murein hydrolases inEscherichia coli |
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Authors: | Joachim-Volker Höltje |
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Institution: | (1) Abteilung Biochemie, Max-Planck-Institut für Entwicklungsbiologie, Spemannstrasse 35, D-72076 Tübingen, Germany |
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Abstract: | Murein hydrolases cleave bonds in the bacterial exoskeleton, the murein (peptidoglycan) sacculus, a covalently closed bag-shaped
polymer made of glycan strands that are crosslinked by peptides. During growth and division of a bacterial cell, these enzymes
are involved in the controlled metabolism of the murein sacculus. Murein hydrolases are believed to function as pacemaker
enzymes for the enlargement of the murein sacculus since opening of bonds in the murein net is needed to allow the insertion
of new subunits into the sacculus. Furthermore, they are responsible for splitting the septum during cell division. The murein
turnover products that are released during growth are further degraded by these hydrolases to products that can be recycled
by the biosynthetic enzymes. As potentially suicidal (autolytic) enzymes, murein hydrolases must be strictly controlled by
the cell, Inhibition of murein synthesis, for example by penicillin, triggers an unbalanced action of murein hydrolases causing
bacteriolysis. InEscherichia coli, 14 different murein hydrolases have so far been identified, includingN-acetylmuramyl-l-alanine amidases,dd-endopeptidases,dd-carboxypeptidases,ld-carboxypeptidases, andN-acetylglucosaminidases. In addition lysozyme-like enzymes, called “lytic transglycosylases,” produce (1→6)-anhydromuramic
acid derivatives by an intramolecular transglycosylation reaction. |
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Keywords: | Peptidoglycan Autolysin Endopeptidase Carboxypeptidase Amidase Lytic transglycoslase Glucosaminidase Penicillin-binding protein Sacculus Multienzyme complex |
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