Peptidoglycan synthesis pathway, what is peptidoglycan?

One is uridine diphosphate (UDP). The disaccharide peptide is first inserted into the peptidoglycan backbone (a molecule containing at least 6 8 peptidoglycan monomers) as a primer at the cell wall growth point, and the polysaccharide chain is extended by a disaccharide unit by transglycosylation. In the second step, the adjacent polysaccharide chains are cross-linked by transpeptidation by transpeptidase. During peptide transinfection, the peptide chain between D-alanyl-D-alanine is broken to release a D-alanyl residue, and then the peptide bond is formed between the free carboxyl group of the penultimate D-alanine and the free amino group of the o-chain glycine pentapeptide to achieve cross-linking.

Two vectors are known, and the synthetic site has been metastasized. Therefore, the biosynthesis of peptidoglycan is divided into three stages: synthesis in the cytoplasm, on the cell membrane and outside the cell membrane. Because peptidoglycan synthesis is not done in one place, it is necessary to have a carrier that can transport and control the structural elements of peptidoglycan in the synthesis process.

The first step in this phase is the elongation of the polysaccharide chain, and N-acetylmuramic acid and muramic acid pentapeptide are bound to the glycophore UDP.

The second stage, the other is bacterial terpene alcohols.

Take the well-understood peptidoglycan synthesis of Staphylococcus aureus as an example.

In the first stage, the disaccharide peptide subunit is formed.

In the third stage, this is a C55 isoprenoid composed of 11 isoprenoid units: the synthesis of muramic acid pentapeptide in the cytoplasm. This phase begins with N-acetylglucosamine-1-phosphate, which is produced from glucose through the following reaction steps:

Starting with N-acetylglucosamine-1-phosphate, later N-acetylglucosamine: the synthesized disaccharide peptide is inserted in the cell wall growth point outside the cell membrane and cross-linked to form peptidoglycan: the peptidoglycan monomer - disaccharide peptide subunit is synthesized from N-acetylmuramic acid pentapeptide and N-acetylglucosamine on the cell membrane.

In this stage, there is a lipid carrier called bacterial terpene alcohol (BCP), which is linked to N-acetylmuramic acid through two phosphate groups, carrying the UDP-N-acetylmuramic acid pentapeptide formed in the cytoplasm to the cell membrane, where it binds to N-acetylglucosamine, and attaches pentapeptide (GLY)5 peptidoglycan to L-Lys.

Peptidoglycan is a multilayer network macromolecular structure formed by the polymerization of acetyl glucosamine, acetyl muramic acid, and four to five amino acid short peptides.

Peptidoglycan, also known as mucocomplex, murein. It is a multi-layer reticulated macromolecular structure composed of disaccharide units, tetrapeptide tails and peptide bridges.

N-acetylglucosamine (also known as NAG) and N-acetylmuramicacid (NAMA) alternately link heteropolysaccharides and peptides of different compositions to form macromolecules that are carefully formed by cross-linking acacia groups with different compositions. Peptidoglycan is a major component of the cell wall of many bacteria.

For example, the peptidoglycan contained in the cell wall of Gram-positive bacteria accounts for 50-80% of the dry weight, which is composed of N-acetylglucosamine and N-acetyl muramic acid connected by -1,4 glycosidic bonds, and the sugar chains are cross-linked by peptide chains to form a stable network structure, the length of the peptide chain is different from that of short-sighted bacteria, and the peptidoglycan contained in the cell wall of Gram-negative bacteria accounts for 5-20% of the dry weight, and its disaccharide units are the same as those of Gram-positive bacteria.

Peptidoglycan. Peptidoglycan) is a cell wall component specific to prokaryotes. A macromolecular complex consisting of several N-acetyl-glucosamine (NAG) and.

N-acetylmuramic acid (N-acetyl

muramic

acid, nam) is high in trouser residue and a few amino acids.

Polymerization of subunits composed of short peptide chains. NAG and NAM are arranged alternately; Linked with -1,4 glucosidic bonds, a peptidoglycan polysaccharide chain is formed, the length of which varies depending on the strain. Each polysaccharide chain has 10 65 disaccharide units (or amino sugars). to peptide bonds.

Linked amino acid short peptides, forming a peptide chain of peptidoglycan. The composition and order of its amino acids are usually L-alanine, D-glutamic acid, L-diamino acid (i.e., L-lysine or diaminopinoheptanetic acid, etc.) and D-alanine. These short peptides pass through a D-lactyl carboxyl group.

Attached to residues of some or all NAM. Adjacent short peptides convert peptidoglycan in a certain way.

The subunits are cross-linked into a repeat structure, gram-positive bacteria.

The sub-monohu position of 75 in the peptidoglycan molecule is criss-crossed and connected, thus forming a three-dimensional spatial grid structure with tightly braided, hard texture and great mechanical strength.

Peptidoglycan, also known as mucocomplex, murein. It is a multi-layer reticulated macromolecule formed by the polymerization of disaccharide units, tetrapeptide tails and peptide bridges, so peptidoglycan is not a polysaccharide.

Peptidoglycan is found in the cell walls of gram-positive bacteria and gram-negative bacteria in eubacteria. It is a multi-layer network macromolecular structure formed by the polymerization of acetyl glucosamine, acetyl muramic acid and four to five aminozaosaic acid short peptides. An oligopeptide chain is elicited from each N-acetylmuramic acid, which is connected to the n-acetyl muramic acid on the adjacent polysaccharide chain, so that the two parallel sugar chains are horizontally connected to form a network, thus forming a layer of peptidoglycan.

1.g-m disaccharide units;

2.Tetrapeptide tail.

Composition: L-ALA + D-Glu + L-Lys + D-Ala for Gram-positive bacteria (e.g., Staphylococcus) and L-Ala + D-Glu + M-DAP + D-Ala for Gram-negative bacteria (e.g., Escherichia coli);

Ligation: -NH2 on L-Ala at the N-terminus of tetrapeptide is linked to the carboxyl group of lactate in M;

3.Peptide bridges.

Composition: There are many variations of peptide bridges, there are more than 100 species, such as, in the peptide bridge, glycine pentapeptide.

Ligation: The N-terminus amino group of glycine pentapeptide is linked to the carboxyl group on the C-terminal D-Ala of the tetrapeptide, and the C-terminal carboxyl group is linked to another four.

Peptide on L-Lys - amino-linked. Gram Y-negative bacteria do not have a special peptide bridge, so the D-ALA of the anterior and posterior peptide tails is directly connected to the M-DAP.

Lysozyme. Antibiotics inhibit peptidoglycan biosynthesis. Conditions for peptidoglycan synthesis: Two main carriers are required, namely uracil diphosphate (UDP) and polypentadiene phosphate (also known as bacterial terpene alcohols).

Peptidoglycan

Peptidoglycan is a multi-layer reticular macromolecular structure formed by the polymerization of acetylglucosamine, acetyl muramic acid and four or five amino acid short peptides.

Macromolecules formed by alternately linking heteropolysaccharides with alternately linked heteropolysaccharides of N-acetylglucosamine (G) and N-acetylmuramic acid (M) with peptides of different compositions. Peptidoglycan is a major component of the cell wall of many bacteria. For example, the peptidoglycan contained in the cell wall of gram-positive bacteria accounts for 50-80% of the dry weight, and the peptidoglycan contained in the cell wall of gram-negative bacteria accounts for 1-10% of the dry weight.

Composition and structural characteristics.

1.g-m disaccharide units;

2.Tetrapeptide tail.

Composition: L-Ala + D-Glu + L-Lys + D-Ala for Gram-positive bacteria and L-Ala + L-DAP + D-Ala for Gram-negative bacteria;

Ligation: -NH2 on L-Ala at the N-terminus of tetrapeptide is linked to the carboxyl group of lactate in M;

3.Peptide bridges.

Composition: There are many variations of peptide bridges, currently with more than 100 species, such as, in the peptide bridge, glycine pentapeptide.

Ligation: The N-terminus -amino group of glycine pentapeptide is linked to the carboxyl group on the C-terminal D-Ala of the tetrapeptide, and the C-terminal carboxyl group is linked to the -amino group of L-Lys on another tetrapeptide. Gram-positive bacteria do not have a special peptide bridge, so the D-Ala of the anterior and posterior peptide tails are directly connected to M-dap.

Lysozyme can hydrolyze the -1,4 glycosidic bonds between G-M, causing holes in the cell wall to disintegrate, thereby killing bacteria. There are large amounts of lysozyme in human tears, and some phages can also secrete lysozyme when infecting the host. Eggs also contain a lot of lysozyme.

Antibiotics inhibit peptidoglycan biosynthesis.

Peptidoglycan, also known as mucopeptide, is the main component of the bacterial cell wall and is a substance unique to the cells of prokaryotes. It is composed of N-acetylglucosamine and N-acetylmuramic acid linked to a glycan backbone by -1,4 glycosids, which are then combined with tetrapeptide side chains and pentapeptide cross-linking bridges. Peptidoglycan is endemic to bacteria and differs from G- bacteria in gram-positive (G+) bacteria.

Macromolecular polymers present in the cell walls of prokaryotes. The backbone is a linear glycan chain composed of N-acetylglucosamine (abbreviated G) and N-acetylmuramic acid (abbreviated M) through alternating -1,4 glycosidic bonds. M is a lactyl ether linked to the C3 position of N acetylglucosamine.

Just on the galacyl group of m, a short peptide chain composed of four amino acid residues is linked. The amino acid composition of the short peptide chain varies from strain to species, including the uncommon D-glutamate, D-alanine, L-diaminopoetadioic acid, and other diamino acids; Among them, L-type and D-type amino acids are arranged alternately. The disaccharides composed of g and m, as well as the tetrapeptide linked to m, are the basic structural units of peptidoglycan (Figure 1).

The length of the glycan chain also varies depending on the culture, ranging from 9 disaccharide units to more than 170 disaccharide units. One disaccharide unit is angstroms, so the total length can range from 100 angstroms to about 1700 angstroms. There are cross-links between the individual tetrapeptide chains. In gram-negative bacteria, most of the peptide chains of two peptidoglycans are directly crosslinked, and the cross-linked peptide chains account for 50 of the total number of peptide chains.

Gram-positive bacteria, on the other hand, are cross-linked by another peptide bridge, such as Staphylococcus aureus, which consists of five glycine pentapeptides, and the cross-linked peptide chains account for 75 100 of the total number of peptide chains (Figure 2). Three-dimensional cross-linking enables peptidoglycan to form a multi-level network structure.

Gram-negative bacteria, because peptidoglycan layers are less (e.g., Escherichia coli is 3 layers, thickness is about 2 3 nanometers), the degree of cross-linking is low, so the network structure is loose; Gram-positive bacteria, on the other hand, have a high degree of cross-linking and a tight reticular structure due to the large number of peptidoglycan layers (e.g., about 10 layers of Staphylococcus aureus and about 20 layers of Bacillus subtilis, with a thickness of up to 10 50 nanometers).

The differences between these two types of bacteria in peptidoglycan content, thickness, layer and degree of cross-linking, coupled with the differences in other components of the cell wall, are reflected in the staining properties, sensitivity to lysozyme and substance permeability. A small number of bacteria, such as halophiles, have a special cell wall structure and do not contain peptidoglycan.

Several antimicrobials, such as penicillin, vancomycin, bacitracin, fosfomycin, cycloserine, and persistent mycin, act on different steps of peptidoglycan biosynthesis to inhibit peptidoglycan biosynthesis and thus inhibit bacterial growth. Lysozyme breaks the glycan chain of peptidoglycan, destroys the cell wall structure, and kills bacteria.

Peptidoglycan is a multi-layer reticular macromolecular structure formed by the polymerization of disaccharide units, tetrapeptide tails and peptide bridges.

Macromolecules formed by alternately linking heteropolysaccharides to N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAMA) with peptides of different compositions. Peptidoglycan is a major component of the cell wall of many bacteria. For example, the peptidoglycan contained in the cell wall of gram-positive bacteria (G+) accounts for 50-80% of the dry weight, which is connected by N-acetylglucosamine and N-acetylmuramic acid through -1,4 glycosidic bonds, and the sugar chains are cross-linked by peptide chains to form a stable network structure, the length of peptide chains varies from one species to another, and the peptidoglycan contained in the cell wall of gram-negative bacteria (G-) accounts for 5-20% of the dry weight, and its disaccharide units are the same as those of Gram-positive bacteria, but the third tetrapeptide tail is not L-Lys, but racemic diaminopinoheptanetic acid.

The peptidoglycan backbone is a linear glycan chain composed of N-acetylglucosamine (abbreviated G) and N-acetylmuramic acid (abbreviated M) alternately linked by -1,4 glycosidic bonds. M is a lactyl ether linked to the C3 position of N acetylglucosamine. It's just in the lactyl group of m.

, a short peptide chain consisting of four amino acid residues is linked. The amino acid composition of short peptide chains varies from strain to culture, including the uncommon D-glutamate.

d Alanine.

L-diaminopinoheptanedic acid and other diamino-band acids; Among them, L-type and D-type amino acids are arranged alternately.