Autolytic enzymes

Mode of action Interferes with bacterial cell wall synthesis during active multiplication, causing cell wall death and resultant bactericidal activity Inhibits bacterial cell wall synthesis by binding to one or more of the penicillin-binding proteins, which in turn inhibit the final transpeptidation step of peptidoglycan synthesis in bacterial cell walls bacteria usually lyse from ongoing autolytic enzyme activity... 

The primary mechanism of the action of beta-lactam antibiotics is the inhibition of synthesis of cell membranes of bacteria, which causes them to quickly die. Their initial action is to initiate the work of autolytic enzymes, which destroy cell membranes and cause lysis of the bacteria. 

The purpose of this process is the production of foodstuffs that are shelf stable at ambient temperatures and that have better quality characteristics than the corresponding heat-sterilized products. Radappertization dose of low-acid foods must ensure elimination of the spores of the most resistant bacterial pathogen, C. botulinum. The dose selected for the purpose is around 50 kGy, 12 times of the Z>io value. As the product is intended to be shelf-stable at ambient temperature, while autolytic enzymes have high radiation resist-... 

The theory has been advanced that there exists in the cell a particulate structure somewhat smaller than the mitochondrion, the lyso-some, that contains certain autolytic enzymes in a latent situation. The lysosome theory55,56 is very largely based upon measurements made in sucrose homogenates of rodent liver. Although the results for a-D-mannosidase in this tissue (see Table IV) are not incompatible with the theory, the results for other tissues do not always conform to it. In particular, the contrast between mouse and rat spleen argues against a universal single particle to which a-D-mannosidase is confined. Apart from the results quoted in Table IV, not much work has been done on the intracellular location of a-D-mannosidase. 

All cephalosporins act by inhibiting bacterial cell wall synthesis and are bactericidal. Also the autolytic enzymes in cell wall may be activated leading to bacterial death. 

Another physiological role of both types of teichoic acids is their interaction with autolytic enzymes and the regulation of their activity5> 32). 

Selective inhibition of bacterial cell wall synthesis (penicillins, cephalosporins, bacitracin, vancomycin). Following attachment to receptors (penicillinbinding proteins), p-lactam antibiotics inhibit transpeptidation enzymes and thereby block the final stage of peptidoglycan sysnthesis. This action is followed by inactivation of an inhibitor of autolytic enzymes in the bacterial cell wall. Bacitracin and vancomycin inhibit early stages of peptidoglycan synthesis. 

The biochemical properties of chloroquine and related anti-malarials have been exeonined further. In addition to its inhibition of the biosynthesis of sulfated mucopolysaccharides, chloroquine inhibits irreversibly an autolytic enzyme from bovine cartilage and a rat skin collagenase (at 10 mM). Like hydrocortisone, it inhibits chemotaocis of leukocytes and, to a lesser extent, the phagocytosis process.It also stabilizes lysosomal membranes in vitro. Potential "anti-degenerative" activity is clearly suggested by these properties, but unfortunately the well-known retinopathic effect is further complicated by a delayed symptom. 

Binding to PBPs also results in activation of autolytic enzymes. 

Although other types of resistance may occur (e.g., PBP mutations, autolytic enzyme deficiency, and decreased drug penetration), J3-lactam C-N bond hydrolysis is most significant to clinical resistance. 

C. Mechanisms of Action and Resistance Beta-lactam antibiotics are bactericidal drugs. They act to inhibit cell wall synthesis by the following steps (Figure 43 2) (1) binding of the drug to specific receptors (penicillin-binding proteins PBPs) located in the bacterial cytoplasmic membrane (2) inhibition of transpeptidase enzymes that act to cross-link linear peptido-glycan chains which form part of the cell wall and (3) activation of autolytic enzymes that cause lesions in the bacterial cell wall. 

Figure 43-2. Beta-lactams and bacterial cell wall synthesis. The outer membrane shown in this simplified diagram is present only in gram-negative organisms. It is penetrated by proteins (porins) that are penrie-able to hydrophilic substances such as beta-lactam antibiotics. The peptidoglycan chains (mureins) are cross-linked by transpeptidases located in the cytoplasmic membrane, closely associated with penicillinbinding proteins (PBPs). Beta-lactam antibiotics bind to PBPs and inhibit transpeptidation, the final step in cell wall synthesis They also activate autolytic enzymes that cause lesions in the cell wall. Beta-lactamases, which inactivate beta-lactam antibiotics, may be present in the periplasmic space or on the outer surface of the cytoplasmic membrane. (Reproduced, with permission, from Katzung BG [editor]. Basic Clinical Pharmacology, 8th ed. McGraw-Hill, 2001.)...

Piperacillin blocks the attachment of ampicillin to penicillin-binding proteins Ampicillin induces beta-lactamase production Autolytic enzymes are inhibited by piperacillin Ampicillin is bacteriostatic... 

Cephalosporins bind to PBPs and activation of autolytic enzymes is contributory to their bactericidal action... 

In the earlier experiments by Fischer and Bergell it was found that leucyl-alanine was hydrolysed by an extract of pancreas it was not however hydrolysed by pure pancreatic juice. Such extracts probably contain other enzymes, more especially the autolytic enzyme, which produce the hydrolysis the later work of Abderhalden and his coworkers upon the action of enzymes from various organs also show that polypeptides not hydrolysed by pure tiypsin are attacked by these enzymes (see table, p. 48). 

The autolytic enzyme lysozyme, ( enStreptococcus faecium was released in a soluble form from insoluble cell wall-autolytic enzyme complexes by treatment with dilute NaOH at 0 Treatment of cell wall-enzyme complexes, obtained from either exponential-or stationary-phase cells, with 0.008 to 0.01 N NaOH gave maximum yields of autolytic enzyme activity. At a fixed concentration of NaOH, the yield of autolysin increased with increasing wall densities and was accompanied by the release of methylpentose and phosphorus in amounts proportional to the autolysin. Since extraction of wall-enzyme complexes with 4.5 M LiCl at 0 C also removed methylpentose and phosphorus, release of enzyme with NaOH did not appear to result from hydrolysis of covalent linkages. The autolytic enzyme activity released from intact cells, or cell walls, was predominantly in the latent... 

A secondary mechanism of action is a detergent-like effect (103). However, it is unclear whether this merely r esents the cocqierative accumulation of multistate channels or gross multimerisation of cationic peptides in the membrane, and whether this mechanism is relevant to bacterial cell killing, since it has only been demonstrated in nondefinitive experiments in eukaryotic cell lines and model liposomes (103). In contrast, the lysis of bacteria—often at concentrations exceeding the MIC—prob ly arises from the triggering of autolytic enzymes (104). With diese caveats, it is worth considering how cationic peptides interact with membranes. 

A solution of formalin (0.012%) has been shown to induce cell lysis in E.coli, staphylococci and streptococci [195], Autolytic enzymes are presumably not inhibited at such low concentrations, and this action has thus been compared with that of penicillin, a cell wall-acting antibiotic [195],... 

New methods such as the incorporation of temperature-sensitive plasmids for the production of autolytic enzymes should reduce separation costs. The direct... 

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