Ligases are a class of enzymes that catalyse the linking together of two compounds. According to the standard classification of enzymes, which of the following bonds is NOT explicitly listed as being joined by ligases?

Step-by-step solution

According to the standard classification of enzymes, Ligases catalyse the linking together of two compounds. The NCERT explicitly lists the joining of C-O, C-S, C-N, and P-O bonds as examples of reactions catalysed by ligases. The P-N bond is not listed under ligases; instead, it is explicitly mentioned as a bond whose hydrolysis is catalysed by the enzyme class Hydrolases. Therefore, the P-N bond is the correct answer as it is not joined by ligases. Answer: P-N bond