ACP1 encodes low-molecular weight protein tyrosine phosphatase (LMPTP), a polymorphic enzyme with three common codominant alleles (*A, *B, *C) that produce two major isoforms (F and S) with varying activity levels 1. Despite UniProt annotations suggesting lack of phosphatase activity, functional evidence demonstrates ACP1 possesses tyrosine phosphatase activity 2. ACP1 regulates cellular signaling by dephosphorylating key metabolic enzymes; specifically, it promotes glutathione synthesis in prostate cancer cells by dephosphorylating glutathione synthetase at Tyr270 3. Genome-wide association studies identify ACP1 as a locus influencing pubertal timing, with earlier puberty causally associated with accelerated aging and cardiovascular disease risk 4, and as a contributor to kidney function variation, with ACP1 knockdown in zebrafish causing glomerular abnormalities and impaired renal function 5. ACP1 genetic variants show population-level associations with malarial disease resistance, with higher S isoform concentrations conferring protection against malaria 1. Clinically, ACP1 overexpression in prostate tumors correlates with poor survival outcomes, and LMPTP inhibition slows tumor growth and bone metastasis while sensitizing cancer cells to oxidative stress 3. ACP1 expression is dysregulated in hepatocellular carcinoma, emerging as a prognostic biomarker 6.