Thymidine 5′-diphosphate (dTDP) sodium is the key product of pyrimidine synthesis in organisms. Thymidine 5′-diphosphate sodium is produced by thymidylate kinase (TMPK) catalyzed phosphorylation of 5′-thymidine monophosphate (dTMP), which requires ATP and Mg²⁺. Thymidine 5′-diphosphate sodium is further catalyzed by TMPK to thymidine 5′-triphosphate (dTTP). TMPK activity can be detected by measuring the level of Thymidine 5′-diphosphate^[1][2].