Bacterial cell wall biosynthesis pathway

Figure 1. The bacterial cell wall biosynthesis pathway.

Figure 11 Sequential murein biosynthetic pathway, the early steps of the bacterial cell wall biosynthesis.

This can be achieved in a variety of ways. For instance, it is possible to inhibit an essential pathway in the pathogen that does not exist in the host. o-Cycloserine (1) (Fig. 17.1), for example, inhibits alanine race-mase, an enzyme involved in bacterial cell wall biosynthesis and not found in humans (8, 9). D-Cycloserine is active against a broad spectrum of both gram-positive and gramnegative bacteria (10), but plays its major role in the treatment of tuberculosis (11). Conversely, even if both host and pathogen contain the same enzymes, it may be possi-... 

The pathway from simple molecules to the peptidoglycan of the bacterial cell wall is lengthy and complex. Many of the details are well known but need not concern us here. Suffice it to say that long carbohydrate chains are synthesized, subsequently decorated with shorter amino acid chains, and these are finally cross-linked to provide a strong strnctnre. It is this final cross-linking step that is inhibited by the p-lactam antibiotics. The consequence is that cell wall biosynthesis cannot be completed and cell death ensnes. Again, the mammalian host carries out no similar reactions so that similar consequences do not ensne for the host orgaiusm. 

Bacteria synthesize lysine through one of three different pathways that are not present in mammals. " An intermediate in these pathways, wj ro-diaminopimelic acid (mDAP), is also an essential component of the bacterial cell wall. " " Consequently, the enzymes in these pathways are targets for the development of antibiotics for treatment of Gram-negative and Gram-positive bacterial infections. The enzyme DapE catalyzes the hydrolysis of N-succinyl-L,L-diaminopimelic acid to form L,L-diaminopimelic acid and succinate in the succinylase pathway of lysine biosynthesis (Figure 6(i)). 

Microorganisms are proficient in synthesizing a large number of polysaccharides. The pathways for their biosynthesis are similar to the procedures that take place for the formation bacterial cell wall. It is anticipated that there are well over 100 enzymatic reactions, directly or indirectly involved in the synfliesis of polysaccharides. Initially with glucose, suitable sugars (by transforming glucose to others) are included in the formation of polysaccharides. 

A large number of cellular processes and biosythetic pathways of eukaryotic cells are compartmentalized and restricted to specific membranes. Mitochondria and chloroplasts are two cases in point. In prokaryotic cells, many of the same functions are performed by a single membrane. The transport of metabolites and ions, oxidative phosphorylation, photosynthesis, phospholipid biosynthesis, and the synthesis of cell-wall constituents are a few examples of processes carried out by enzyme systems localized in the bacterial plasma membrane (Chapters... 

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