Mechanism of peptidoglycan synthesis in E. coli

Question 1

What is the 1st step

Answer 1

synthesis of peptidoglycan subunits in cytoplasm

Question 2

what is the 1st step a

Answer 2

NAM and NAG are synthesized, each one is covalently linked to UDP

Question 3

what is the 1st step b

Answer 3

5 aa added to NAM-UDP. synthesis of pentapeptide does not use ribosomes. each step has its on enzyme and uses ATP

Question 4

What is the 2nd step

Answer 4

assembly of subunit and transfer to bactoprenol phosphate

Question 5

what is the 2nd step a

Answer 5

a phosphate-NAM-pentapeptide is transfer from UDP to bactoprenol-phosphate. UMP is recycle

Question 6

what is the 2nd step b

Answer 6

A NAG is linked to NAM, the UDP is recycled. subunit is complete

Question 7

what is the 2nd step c

Answer 7

bactoprenol diphosphate moves subunit across the PM

Question 8

what is the 3rd step

Answer 8

covalent linkage of the subunit to existing peptidoglycan requires periplasmic enzyme

Question 9

what is the 3rd step a

Answer 9

autolysins opens a region in exisiting peptidoglycan

Question 10

what is the 3rd step b

Answer 10

transglycosylase links NAM-NAG of subunit into glycan chain

Question 11

what is the 3rd step c

Answer 11

transpeptidase links peptides, called trans-peptidation. no ATP outside cytoplasm. enzyme uses nrg released by cleavage of terminal D-ala-D-ala of one pentapeptide to form a new peptide bond

Question 12

what is the 3rd step d

Answer 12

new bond is formed btwn free amino group of DAP and carboxyl group of remaining D-ala, peptide is now tetra peptide

Question 13

what is the 4th step

Answer 13

bactoprenol diphosphate is flipped across membrane to transport another subunit. during this process has one phosphate removed