XYLB encodes xylulokinase, an enzyme that catalyzes the phosphorylation of D-xylulose to D-xylulose 5-phosphate (Xu5P), playing a crucial role in pentose phosphate pathway metabolism 1. The gene consists of 18 exons spanning approximately 28 kb on chromosome 3.3 1. XYLB functions as a tumor suppressor by producing Xu5P, which enhances CD8+ T cell cytotoxicity and reduces lung colonization in cancer models 2. The Xu5P product promotes antitumor immunity by facilitating uptake into CD8+ T cells via SLC35E2 transporter, subsequently intensifying pentose phosphate pathway and glycolysis for energy balance 2. In intestinal fibrosis associated with Crohn's disease, XYLB activity generates Xu5P that promotes extracellular matrix synthesis through epigenetic upregulation of collagen transcription 3. The enzyme's activity is regulated by circPLCE1, which directly binds XYLB and competitively inhibits its enzymatic function 3. Clinically, elevated XYLB expression correlates with enhanced CD8+ T cell efficacy and reduced metastasis 2, while XYLB has been identified as a potential metabolism-related biomarker in osteosarcoma prognosis 4.