Petidoglycan Synthesis Flashcards
Whats the difference I. The amount of peptidoglycan content between g pos and g neg bacterial cell walls ?
G pos have about 90% peptidoglycan in their cell wall where as g beg have only about 5-10%.
What is found in the glycan portion of the molecule ?
This is the sugar portion and is the same across species. It forms the back bone and is comprised of N-acetylglucosamine (NAG) and N-acetylmeuramic acid (NAM). These alternate and are joined by glycosidic bonds.
What is the structure of the peptide portion of peptidoglycan ?
Amino acids connected by peptide linkages l, variations occur. Alternating d and l amino acids. These amino acids are attached to NAM units. Variations occur whenDAP is found.
How are single chains of peptidoglycan linked ?
Can either be peptide bridges or direct bridges.
How is NAG formed ?
Glucose> fructose-6-P>reacts with glutamate and acetyl-CoA> NAG
How is NAM formed ?
NAG + uridine triphosphate (UTP)> NAG-uridinediphosphate (UDP)>reacts with phosphoenolpyruvate> N-acetylmeramic acid-UDP> NAGM
what happens in stage 2 of the synthesis of PG ?
The UDP sugar links (made in step one) are then transferred to lipid carriers.
what is the NAM pentapeptide transferred to ?
bactoprenol-phophate
what is bactoprenol- phosphate found as in the cm?
it is foun d as pyrophosphate and must be dephosphorylated before it can act a s a carrier.
What and how is NAG transferred ?
NAG is transferred to the NAM-bactoprenil-pentapeptide, creating NAG-NAM- bactoprenol pentapeptide.
What happens when NAG and NAM have been picked up by the carriers ?
PG subunits are released on to existing cell wall.
What is the final stage of PG synthesis ?
The formation of peptide linkages between adjacent glycan chains. Formed between exsisting cell and newly formed PG
What is the enzyme that makes the final peptide bonds ?
Transpeptidase
