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Sulfadrug As Antimetabolites

Sulfonamides, or sulfa drugs, act as antimetabolites by competing with para-aminobenzoic acid (PABA) for incorporation into folic acid. Bacteria must synthesize their own folic acid from PABA, as folic acid cannot cross their cell walls. Sulfa drugs mimic the structure of PABA and are incorporated by bacteria into the folic acid synthesis pathway instead of PABA, inhibiting the final step and preventing folic acid production. This metabolic interference was a pioneering concept in antimicrobial treatment and established sulfa drugs as effective antimetabolites.

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Rajarshi Patel
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54 views2 pages

Sulfadrug As Antimetabolites

Sulfonamides, or sulfa drugs, act as antimetabolites by competing with para-aminobenzoic acid (PABA) for incorporation into folic acid. Bacteria must synthesize their own folic acid from PABA, as folic acid cannot cross their cell walls. Sulfa drugs mimic the structure of PABA and are incorporated by bacteria into the folic acid synthesis pathway instead of PABA, inhibiting the final step and preventing folic acid production. This metabolic interference was a pioneering concept in antimicrobial treatment and established sulfa drugs as effective antimetabolites.

Uploaded by

Rajarshi Patel
Copyright
© Attribution Non-Commercial (BY-NC)
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as DOCX, PDF, TXT or read online on Scribd
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Q: 1 How sulfa drugs act as antimetabolites in antineoplastic agent section

Sulfonamides or Sulfa Drugs as Antimetabolites: The sulfonamides are synthetic antimicrobial agents with a wide spectrum encompassing most gram-positive and many gram-negative organisms. These drugs were the first efficient treatment to be employed systematically for the prevention and cure of bacterial infections. Their use introduced and substantiated the concept of metabolic antagonism. Sulfonamides, as antimetabolites, compete with para-aminobenzoic acid (PABA) for incorporation into folic acid. All cells require folic acid for growth. Folic acid (as a vitamin is in food) diffuses or is transported into human cells. However, folic acid cannot cross bacterial cell walls by diffusion or active transport. For this reason bacteria must synthesize folic acid from p-aminobenzoic acid. This has lead to the discovery of many useful drugs which are effective for diuretics, antimalerial and leprosy agents, and antithyroid agents. The basic structure of sulfonamide cannot be modified if it is to be an effective competitive "mimic" for p-aminobenzoic acid. Essential structural features are the benzene ring with two substituents para to each other; an amino group in the fourth position; and the singly substituted 1-sulfonamido group. Normally folic acid is synthesized in two steps in bacteria by the top reaction on the left. If A sulfa drug is used, the first enzyme is not to specific and can use the sulfonamide in the first reaction. This reaction produces the product containing pteridine and the sulfa drug. The next and final step is the reaction PABA + with glutamic acid to make folic acid. If the sulfa drug has been substituted for the PABA, then the final enzyme is inhibited and no folic acid is produced.

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