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Peptidoglycan or murein is a unique large macromolecule, a polysaccharide, consisting of sugars and amino acids that forms a mesh-like layer (sacculus) that surrounds the bacterial cytoplasmic membrane. [1] The sugar component consists of alternating residues of β-(1,4) linked N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM).
Fluorescent D-amino acids (FDAAs) are D-amino acid derivatives whose side-chain terminal is covalently coupled with a fluorophore molecule. [1] FDAAs incorporate into the bacterial peptidoglycan (PG) in live bacteria, resulting in strong peripheral and septal PG labeling without affecting cell growth.
Peptidoglycan consists of cross-linked amino acids and sugars which form alternating amino sugars: N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM). Endo-β-N-acetylglucosaminidase lysins cleave NAGs while N-acetylmuramidase lysins (lysozyme-like lysins) cleave NAMs.
N-Acetylmuramic acid (MurNAc) is part of the peptidoglycan polymer of bacterial cell walls. MurNAc is covalently linked to N-acetylglucosamine and may also be linked through the hydroxyl on carbon number 4 to the carbon of L-alanine. A pentapeptide composed of L-alanyl-D-isoglutaminyl-L-lysyl-D-alanyl-D-alanine is added to the MurNAc in the ...
Lysozyme (EC 3.2.1.17, muramidase, N-acetylmuramide glycanhydrolase; systematic name peptidoglycan N-acetylmuramoylhydrolase) is an antimicrobial enzyme produced by animals that forms part of the innate immune system. It is a glycoside hydrolase that catalyzes the following process:
It degrades the peptidoglycan by targeting the β-1,4-glycosidic bonds that connect the alternating amino sugars in which it is composed of. [8] This degradation of the glycosidic bonds within peptidoglycan cause the sugars to separate and inhibit the structural integrity of the peptidoglycan and the bacteria.
Schematic of typical Gram-positive cell wall showing arrangement of N-Acetylglucosamine and N-Acetylmuramic acid; Teichoic acids not shown. The Gram-positive cell wall is characterized by the presence of a very thick peptidoglycan layer, which is responsible for the retention of the crystal violet dyes during the Gram staining procedure.
Muramic acid is an amino sugar acid. In terms of chemical composition, it is the ether of lactic acid and glucosamine . It occurs naturally as N -acetylmuramic acid in peptidoglycan , whose primary function is a structural component of many typical bacterial cell walls .