Penicillin is less toxic to humans and animals, what is the reason?

Penicillin. The mechanism is to act on the cell wall of bacteria, interfering with the synthesis of the bacterial cell wall, because the cell wall is to maintain the osmotic pressure of bacteria.

Bacteria without a cell wall cannot survive.

Humans and animals themselves do not have a cell wall and do not need a cell wall to maintain osmotic pressure, so penicillin is less toxic to humans and animals.

Penicillin, also known as penicillin, is a general term for a class of antibiotics with betalactam rings, which was first isolated by Fleming from Penicillium spot, and later obtained high-yielding strains from Penicillium flavona. The mechanism of action of penicillin is to act on the cell wall of bacteria, especially gram-positive bacteria, the cell wall of bacteria is formed by the cross-linking of N-acetylmuramic acid and N-acetylglucosamine, penicillin can compete with N-acetylglucosamine cross-link, resulting in the cell wall can not be synthesized, so the bacteria do not have a cell wall that can play a supporting role and maintain the shape, so it will rupture and die. Human and animal do not have a cell wall, so it will not have an effect on people and animals, note that the cell wall of bacteria is different from that of plants, which are composed of pectin and cellulose, and the cell wall of bacteria is composed of N-acetylmuramic acid and N-acetylglucosamine, which can be called peptidoglycan in general.

After penicillin enters the human body, its main role is to interfere with the synthesis of bacterial cell walls. Human and animal cells do not have a cell wall and are less toxic than bacteria.

Penicillin has bactericidal and bacteriostatic effects, but can also kill beneficial bacteria or animal cells if abused.

The antimicrobial effect of penicillin is associated with inhibition of cell wall synthesis. The cell wall of bacteria is a thick, tough film that resists external pressure and maintains the shape of the cell. Inside the cell wall is the cell membrane, which is surrounded by cytoplasm.

The cell wall of bacteria is mainly made up of polysaccharides and also contains proteins and lipids. The composition of the cell wall of gram-positive bacteria is peptidoglycan 50 80 (1 10 for gram-negative bacteria) of the dry weight of the cell wall, teichoic acid, lipoproteins, polysaccharides and proteins. Among them, peptidoglycan is a reticular biological macromolecule containing acetylglucosamine and short peptide units, and a key enzyme, transpeptidase, is required in its biosynthesis.

The site of action of penicillin is this transpeptidase. It has been proved that the highly reactive peptide bond on the phthalamine ring in penicillin is covalently attacked by the nucleophilic attack of the hydroxyl group of the serine residue on the active site of transpeptidase to form a penicillium thiazolyl-enzyme complex, thereby irreversibly inhibiting the catalytic activity of the enzyme. By inhibiting transpeptidase, penicillin inhibits the synthesis of the cell wall, reduces the anti-osmotic pressure of bacteria, and causes the bacteria to deform, rupture and die.