Isoniazid blocks the gene for an enzyme that forms mycolic acid. What would you expect to be the most susceptible to effect of this antimicrobial agent?
A) Most Gram positive cells
B) acid fast bacteria
C) many archaea
D) Fungal cells
E) most gram negative cells
Answer
B) acid fast bacteria
the drug itself is a prodrug and is converted into its active form by the enzyme catalase-peroxidase and the drug inhibits mycolic acid synthesis, thereby blocking mycobacterium cell wall synthesis.
Explanation
In this case, the drug targets the enzymes necessary for the biosynthesis of molecular building blocks and assembly of the mycobacterial cell wall core and mycobacterial outer membrane (MOM) and the microbe whih do have mycolic acid in large amount is the acid-fast bacteria. Thus we can conclude that the drug itself is a prodrug and is converted into its active form by the enzyme catalase-peroxidase and the drug inhibits mycolic acid synthesis, thereby blocking mycobacterium cell wall synthesis.
