ENTPD4 Full-Length MS Protein Standard (NP_004892), Labeled with [U- 13C6, 15N4]-L-Arginine and [U- 13C6, 15N2]-L-Lysine, was produced in human 293 cells (HEK293) with fully chemically defined cell culture medium to obtain incorporation efficiency at Creative-Proteomics. This gene encodes a member of the apyrase protein family. Apyrases are enzymes that catalyze the hydrolysis of nucleotide diphosphates and triphosphates in a calcium or magnesium-dependent manner. The encoded protein is an endo-apyrase and may play a role in salvaging nucleotides from lysosomes. Alternatively spliced transcript variants encoding multiple isoforms have been observed for this gene, and these isoforms may differ in divalent cation dependence and substrate specificity.