Which of the Following is Most Often Found in Proteins

Question

Which of the following is most often found in proteins?
A) D-amino acids
B) L-amino acids
C) an equal amount of D- and L-amino acids
D) amino acids with the $\alpha$-carbon exclusively having an R absolute configuration
E) amino acids with the $\alpha$-carbon exclusively having an S absolute configuration

Accepted Answer

Proteins are primarily composed of L-amino acids. This is due to the fact that the enzymes responsible for protein synthesis in living organisms are stereospecific, selecting for L-amino acids over their D-counterparts.