Cyclic Nucleotides as Mediators of Acinar and Ductal Function

Abstract

Cyclic nucleotides, like other nucleotides, are composed of three functional groups: a ribose sugar, a nitrogenous base, and a single phosphate group. There are two types of nitrogenous bases: purines (adenine and guanine) and pyrimidines (cytosine, uracil and thymine). A cyclic nucleotide, unlike other nucleotides, has a cyclic bond arrangement between the ribose sugar and the phosphate group. There are two main groups of cyclic nucleotides: the canonical or well-stablished and the non-canonical or unknown function cyclic nucleotides. The two well-established cyclic nucleotides are adenosine 3’,5’-cyclic monophosphate (cyclic AMP) and guanine-3’,5’cyclic monophosphate (cyclic GMP). Both cyclic AMP and cyclic GMP are second messengers. The non-canonical cyclic nucleotides include the purine inosine 3’,5’-cyclic monophosphate (cyclic IMP), xanthosine 3’,5’-cyclic monophosphate (cyclic XMP) and the pyrimidine cytidine 3’,5’-cyclic monophosphate (cyclic cCMP), uridine-3’,5’-cyclic monophosphate (cyclic UMP), thymidine 3’,5’cyclic monophosphate (cTMP) (128). An overview of the non-canonical cyclic nucleotides is provided in Section 3.