Why are we made up of L-amino acid proteins?

first things first: If we were made up of D-Amino-Acids and left-spinning DNA, nothing would differ from what we are now. read more

The theory so far is (AFAIK), that someday the amount of L-amino acids was higher and in a process of autocatalysis, this amount increased exponentially until the beginning of first primitive lifeforms which were dependent of L-aminoacid-Proteins. So yes, we are made up of one stereoisomer by chance and if there are any alien lifeforms on some other planet which have developed independently from us, if they use the principle of DNA and Aminoacids, chances are 50:50 they use D-Aminoacids. read more

I think the prevalence of L-amino acids in biological systems is a quirk of our evolutionary history; there's no reason D-amino acids wouldn't work chemically, but once early life forms started building proteins out of L-amino acids, L-amino acids became abundant an it became selectively advantageous to use L-amino acids because then you could use the amino acids you obtained by eating someone else. read more

The question the OP is asking, framed in your answer, is"why are enzymes stereospecific for L-amino acids and not D-amino acids." Theres a wrong way to answer this question (because life uses L-aa, which is a tautology) and the"right" way to answer the question, which is no one knows. read more

Why are only L amino acids found in nature. Discussion in 'MCAT Study Question Q&A' started by mackdaddy, Sep 6, 2011. read more