Why amino acid stereochemistry always L-configuration

[Kglocc]

Any known reasons, research, or theories about why earthly amino-acids exist in the L-configuration and have not been found in D-configuration naturally??

 

[Borek]

They do exist in D-configuration, although rarely.

http://en.wikipedia.org/wiki/Amino_acid#Isomerism

 

[chemisttree]

There are many theories. Who knows?

Try these tasty bits for some theories. You need to go to the library to see them, of course.

Nature 389 265 (1997)
Proc. Natl. Acad. Sci. USA 106(14) 5487 (2009)
Angew. Chem. Int. Ed. 38(23) 3418 (1999)
Chem. Rev. 98(7) 2391 (1998)
Mendeleev Commun. 13(3) 129 (2003)
Angew. Chem. Int. Ed. 41(24) 4618 (2002)

 

[Moogie]

Most naturally occurring amino acids are L amino acids. Proteins made from L-amino acids are called left-handed proteins. Homochirality of amino acids is important because it ensures uniformity of protein structure. In other words, proteins made of L-amino acids always fold the same way whereas proteins made from a mixture of L and D amino acids would not have the same structure. This is important for many reasons but the most important is probably recognition by enzymes.

I don't know if this is proved or just a theory

 

[Borek]

In other words, proteins made of L-amino acids always fold the same way whereas proteins made from a mixture of L and D amino acids would not have the same structure.

I think it depends on what you mean by "mixture of L and D amino acids". If you mean mixture in which amino acid is in the form of racemic mixture, and D and L forms are selected at random during peptide synthesis - you are probably right. If you mean mixture containing L and D amino acids, but each given amino acid has always the same conformation - you are probably wrong.

But that's just my guess.

 

[Kglocc]

Thanks brains, I appreciate the sources chemisttree.
I checked them all out. I had heard of the meteorite idea. But my gut was telling me that EM radiation must play a role, and now I have proper research to support.