Are individual molecules toxic or are polypeptides/ proteins toxic?

[Elite Engineer]

I know some compounds are toxic when they are metabolized (i.e. amygdalin in apple seeds is converted to cynanide via digestion).

 

But what would cause a protein to be toxic? They shouldn't be toxic because of what they're metabolized into, b/c they're mainly linked amino acids. Is their toxicity derived from their specific conformation/ properties..like ricin?

 

I guess what i'm trying to ask is, are proteins nontoxic when they're denatured (i.e. no conformation) or are they still toxic even when denatured b/c of their metabolic product.

 

~EE

[BabcockHall]

I don't think I can give a comprehensive answer, but some proteins are toxic because they have enzymatic or other biological activities; cholera toxin comes to mind in that regard.

[foxy john]

Proteins are toxic because of their structure and conformation. Exceptions could be the metallo proteins where a toxic metal is bound to the protein, but that is the metal being toxic, not the protein. A denatured protein could be toxic if the shape is correct/incorrect, they still have a conformation, albeit a different one to normal.

[Itoero]

The polyglutamine diseases are a group of neurodegenerative disorders caused by expanded cytosine-adenine-guanine repeats encoding a long polyglutamine tract in the respective proteins. So in this case, extra amino-acids (glutamine) alters the conformation/composition of a protein and causes harmful/toxic effects.

Edited September 23, 2016 by Itoero