What is the function of ?
a. they are central to the re-synthesis of nucleotides from bases in salvage reactions.
b. they mediate the degradation of amp.
c. they are involved in the reversible reactions of purine salvage.
d. they mediate the degradation of imp. e. they are competitive inhibitors employed in the salvage of purine nucleotides.

a. they are central to the re-synthesis of nucleotides from bases in salvage reactions.

Explanation:

are the enzymes that are involved in salvage pathways to reuse the free purines and pyrimidines to make nucleotides. Metabolic degradation of nucleotides releases purines and pyrimidines which in turn enter the salvage pathway to be reused in the formation of new nucleotides. These metabolic pathways that make new nucleotides by reusing the free purines and pyrimidines are called salvage pathways.

Example: Adenosine is the enzyme that catalyzes the formation of adenine nucleotide from free adenine and PRPP (5-phosphoribosyl-1-pyrophosphate).