Case: I am writing a summary for a class in protein structure and function, and was asked to describe some different ways that peptides are synthesized (that does not involve the ribosome). I understand that glutathione is a tri-peptide consisting of L-cystine with a "gamma" bond to L-glycine which is then bound to glutamic acid.
Problem: Why is it that the ribosome cannot produce this peptide? What is special about the peptide-gamma-bond?
My reasoning: The peptide is too short, meaning that the large ribosome complex cannot bind to mRNA of this length as it need many different binding spots in order for the large and small subunit to come together. Also, the "gamma" bond is very special, and the ribosome can only produce peptides with the "Standard" peptide bonds.
Is this correct, and is there something else I am missing?
Does the "gamma" bond relate to the fact the glutathione is not that easily degraded by peptidases in the cytosol?