This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
True about Isopeptide bond: 
Select and explain. 
A. It makes protein resistant, B. Bond is formed b/w carboxyl terminus of one protein and the amino group of a lysine residue on another, C. Involves in post-transcriptional modification of protein and Enzyme acts as catalyst for the bond formation both, D. All
D: All
Answer: D: All 
Explanation: All i.e. (It makes protein resistant, Bond is formed b/w carboxyl terminus of one protein and the amino group of a lysine residue on another, Involves in post-transcriptional modification of protein, Enzyme acts as catalyst for the bond formation)