Antibiotics: Cell wall synthesis inhibitors-Penicillin

Here is my way to remember the type of cell wall synthesis inhibitors, but it is in chinese.

CW C C MB P. -宗伟 常常 慢 半 拍

CW- Cell wall (cell wall inhibitors)

C -cephaloporins

C-carbapenems

MB-monobactam

P- penicillin.

The mechanism of penicillin(in short)

-binds to penicillin binding protein (PBPs)=>inhibit transpeptidase-catalysed reaction=>hinder the formation of crosslink which is essential for  bacterial cell wall integrity. 

The following tables summarises the types, examples and spectrum of penicillin. 

1. The side effects of penicillin includes:

• hypersensitivity
• GI distress (for ampicillin-diarrhea is common)
• bone marrow suppression, anaemia
• renal impairment

2. Interactions

-probenecid increases blood level of penicillins.

3. Bacterial Resistance

-penicillin is degraded by beta-lactamase produced by bacteria.

4. Structure Activity Relationship (covered in Medicinal Chemistry, Sem 4)

notes from Dr.Arjun: Drugs that affect microbial cell walls.

Parent compounds: penicillin G

There are some disadvantages of penicillin G. To improve the properties, some changes can be made. 

5. Allergic reaction

• due to the presence of impurities called penicilloyl proteins obtained during their biosynthesis.

- these penicilloyl proteins are formed by reaction of penicillins, their degraded products & rearranged products with lysine amino groups of proteins of strains.

• Ampicillin-allergic reactions due to the presence of polymeric impurities having antigenic properties.

- ampicillin undergoes pH dependent polymerization reaction -between amino group of acyl side chain of one molecule & beta-lactam carbonyl carbon atom of second molecule.