For example, PHGDH, LDHA, glutamine synthetase, and thymidine kinase 1 (TK1) can regulate the activity, stability, or function of other proteins through protein‐protein interaction to support cancer progression, independently of their metabolic enzyme activities.[8] Deciphering the moonlighting functions (including noncanonical enzymatic activities and nonenzymatic functions) of metabolic enzymes or other enzymes will deepen our understanding of the mechanisms of cancer progression from a new perspective, and lead to the development of novel therapeutic strategies in cancer. The gene discussed is TK1; the disease is cancer.