Extracellular purine metabolism

A variety of nucleotides and the nucleoside adenosine can act as extracellular signaling substances. Their function is terminated by extracellular degradation via surface-located enzymes. The breakdown products may be recycled. This review discusses recent developments in the cellular and molecular biology of enzymes involved in extracellular purine metabolism, including diadenosine polyphosphate hydrolase, ATP-diphosphohydrolase (apyrase), nucleotide pyrophosphatase, 5′-nucleotidase, alkaline phosphatase, NAD-glycohydrolase, and adenosine deaminase. The potential of the surface-located enzymes for ADP-ribosylation and phosphorylation of extracellular proteins is also briefly discussed. Drug Dev. Res. 39:337–352, 1996.