Why are D amino acids toxic more than one answer may be corr

Why are D amino acids toxic? (more than one answer may be correct)

a) because if a mixture of D- and L-amino acids are incorporated into a single polypeptide, alpha helices cannot be formed.

b) because they disrupt alpha helices and beta sheets

c) because D-amino acids are oxidized once they enter the cell and become unable to make peptide bonds.

d) because D-amino acids make left handed helices

Solution

The options B and D are correct. This is because the D-amino acids are the mirror images of L-amino acids. The steric hindrances that favor right handed helix in L-amino acids and prevent left-handed helix in L-amino acids get reversed and instead favor left-handed helices and prevent right handed helixes in D-amino acids. This causes a difference in the metabolism of the molecule formed with the D-amino acids creating toxicity in nature.