Although inhibition of the transpeptidase just described is demonstrably important, there are additional, related targets for the actions of penicillins and cephalosporins; these are collectively termed penicillin-binding proteins (PBPs). All bacteria have several such entities; for example, S. aureus has four PBPs, whereas Escherichia coli has at least seven. The PBPs vary in their affinities for different b -lactam antibiotics, although the interactions eventually become covalent. The higher-molecular-weight PBPs of E. coli (PBPs 1a and 1b) include the transpeptidases responsible for synthesis of the peptidoglycan. Other PBPs in E. coli include those that are necessary for maintenance of the rodlike shape of the bacterium and for septum formation at division. Inhibition of the transpeptidases causes spheroplast formation and rapid lysis. However, inhibition of the activities of other PBPs may cause delayed lysis (PBP 2) or the production of long, filamentous forms of the bacterium (PBP 3). The lethality of penicillin for bacteria appears to involve both lytic and nonlytic mechanisms. Penicillin’s disruption of the balance between PBP-mediated peptidoglycan assembly and murein hydrolase activity results in autolysis. Nonlytic killing by penicillin may involve holin-like proteins in the bacterial membrane that collapse the membrane potential (Bayles, 2000).
The therapy of rheumatism began thousands of years ago with the use of decoctions or extracts of herbs or plants such as willow bark or leaves, most of which turned out to contain salicylates. Following the advent of synthetic salicylate, Felix Hoffman, working at the Bayer company in Germany, made the acetylated form of salicylic acid in 1897. This drug was named "Aspirin" and became the most widely used medicine of all time. In 1971, Vane discovered the mechanism by which aspirin exerts its anti-inflammatory, analgesic and antipyretic actions. He proved that aspirin and other non-steroid anti-inflammatory drugs (NSAIDs) inhibit the activity of the enzyme now called cyclooxygenase (COX) which leads to the formation of prostaglandins (PGs) that cause inflammation, swelling, pain and fever. However, by inhibiting this key enzyme in PG synthesis, the aspirin-like drugs also prevented the production of physiologically important PGs which protect the stomach mucosa from damage by hydrochloric acid, maintain kidney function and aggregate platelets when required. This conclusion provided a unifying explanation for the therapeutic actions and shared side effects of the aspirin-like drugs. Twenty years later, with the discovery of a second COX gene, it became clear that there are two isoforms of the COX enzyme. The constitutive isoform, COX-1, supports the beneficial homeostatic functions, whereas the inducible isoform, COX-2, becomes upregulated by inflammatory mediators and its products cause many of the symptoms of inflammatory diseases such as rheumatoid and osteoarthritis.