MICI 3119 Lecture Notes - Lecture 2: Teichoic Acid, Glycosidic Bond, Glycan
5 Feb 2018
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Peptidoglycan: composition and structure, synthesis and assembly, inhibitors of cell wall synthesis (antibiotics) Teichoic acid and lipoteichoic acid: surface proteins. Peptidoglycan: single macromolecule, highly cross-linked, surrounds entire cell, provides rigidity. N-acetyl moiety: basic units are n-acetyl-d-glucosamine (nag) and n-acetyl- D-muramic acid (nam): nag and nam are joined by -1,4 glycosidic linkages in long. backbone chains (the -1,4 linkage is sensitive to lysozyme). Nag = glcnac, nam = murnac: peptide component: a tetra-peptide is linked to nam, coli: Three steps: cytoplasmic steps, membrane - associated steps, cell wall steps. Peptidoglycan biosynthesis - cytoplasmic steps a. udp activation of nag b. The first committed step in peptidoglycan synthesis c. to udp-nam (inhibited by phosphomycin) Enzymatic addition of 5 amino acids: last addition is d-ala-d-ala dipeptide (synthesis and addition of. D-ala dipeptide is inhibited by d- cycloserine) d. transfer of udp-nam pentapeptide (park"s nucleotide) to a membrane bound carrier lipid (undecaprenyl phosphate) : formation of. L-alanine is the natural form of alanine c.
