Gram-positive bacteria enzymes

Bacitracin. Bacitracin, a cycHc peptide active against gram-positive bacteria, was discovered in 1943. Bacitracin received dmg certification in 1949 (60—62). Whereas human usage of bacitracin is almost exclusively topical, the vast majority of bacitracin manufactured worldwide is used as an animal feed additive. Reviews of work on bacitracin include its chemistry (63—67), comprehensive aspects (62), medical aspects (62,68), biosynthesis on large enzyme complexes and genetics (69—71), and production (71,72). 

O-phosphotransferases that modify macrolides are produced by highly macrolide resistant E. coli isolates. However, these enzymes have no clinical importance for macrolide resistance in gram-positive bacteria, and gram-negative ones are regarded as naturally resistant [2]. 

Fig. 9.1 Schematic representation of possible mechanisms of resistance in Gram-negative and Gram-positive bacteria. 1, antibiotic-inactivating enzymes 2, antibiotic efflux proteins 3, alteration or duplication of intracellular targets 4, alteration of the cell membrane reducing antibiotic uptake 5, alterations in porins or lipopolysaccharide reducing antibiotic uptake or binding.

Huebner, G. Koenig, S. Koch, M.H.J. Hengstenberg, W. Influence of Phosphoenolpyruvate and Magnesium Ions on the Quaternary Structure of Enzyme I of the Phosphotransferase System from Gram-Positive Bacteria. Biochemistry, 34, 15700-15703 (1995)... 

A study on tire storage stability of penicillin G in milk showed that about 60% could be destroyed within 48 h at 2 C, while 75% could be destroyed at 22 C (22). The loss of penicillin G was attributed to the hydrolytic activity of tlie enzyme -lactamase produced by both gram-negative and gram-positive bacteria of the raw milk. This was confirmed by analogous experimentation with UHT milk, in which penicillin G did not show any decrease under mentioned storage conditions. 

Many antibiotics, which inhibit protein synthesis, do not bind to ribosomes but block any of a variety of vital chemical processes needed for growth. Among them are pseudomonic acid, which inhibits isoleucyl-tRNA synthetase from many gram-positive bacteria.1111/VV Rapamycin, best known as an immunosuppressant (Box 9-F), inhibits phosphoinositide-3-kinase and also phosphorylation of the cap-binding protein 4G, a component of the eukaryotic initiation factor complex (Fig. 29-11 ).ww The bacterial enzyme peptide deformylase, which is absent from the human body, has been suggested as a target for design of synthetic antibiotics. 01... 

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