Differnece between Endotoxin and Exotoxin

Differences Between

Exotoxins and Endotoxins

Toxins and enzymes play important role in pathogenecity. Toxins are of two types:

Exotoxins are usually heat labile proteins secreted by certain species of bacteria which diffuse into the surrounding medium.

Endotoxins are heat stable lipopolysaccharide-protein complexes which form structural components of cell wall of Gram Negative Bacteria and liberated only on cell lysis or death of bacteria.

Some of the differences between 
Exotoxins and Endotoxins are as follows:

S.N.	Exotoxins	Endotoxins
1	Excreted by organisms, living cell	Integral part of cell wall
2	Found in both Gram positive and Gram Negative bacteria	Found mostly in Gram Negative Bacteria
3	It is polypeptide	It is lipopolysaccharide complex.
4	Relatively unstable, heat labile (60°C)	Relatively stable, heat tolerant
5	Highly antigenic	Weakly immunogenic
6	Toxoids can be madeby treating with formalin	Toxoids cannot be made
7	Highly toxic, fatal in µg quantities	Moderately toxic
8	Usually binds to specific receptors	Specific receptors not found
9	Not pyrogenic usually, Toxin Specific	Fever by induction of interleukin 1 (IL-1) production, Shock
10	Located on extrachromosomal genes (e.g. plasmids)	Located on chromosomal genes
11	Filterable	Not so
12	It has no enzymatic activity	It has mostly enzymatic activity
13	Its molecular weight is 10KDa	Its molecular weight is 50-1000KDa
14	On boiling it get denatured.	On boiling it cannot be denatured.
15	Detected by many tests (neutralization, precipitation, etc)	Detected by Limulus lysate assay
16	Examples: Toxins produced byStaphylococcus aureus, Bacillus cereus, Streptococcus pyogenes, Bacillus anthrcis(Alpha-toxin, also known as alpha-hemolysin (Hla))	Examples: Toxins produced by E.coli, Salmonella Typhi, Shigella, Vibrio cholera(Cholera toxin- also known as choleragen)
17	Diseases: Tetanus, diphtheria, botulism	Diseases: Meningococcemia, sepsis by gram negative rods