PHEX is a transmembrane endopeptidase that belongs to the type II integral membrane zinc-dependent endopeptidase family. The protein is thought to be involved in bone and dentin mineralization and renal phosphate reabsorption. Mutations in this gene cause X-linked hypophosphatemic rickets.

The PHEX protein is predicted to have a 20-residue N-terminal cytoplasmic tail, a 27-residue transmembrane domain, and a 702-residue extracellular C-terminal region. The protein belongs to the type II integral membrane zinc-dependent endopeptidase family. PHEX transcripts were identified in human osteosarcoma-derived cells and in differentiated mouse osteoblasts, but not in immature mouse preosteoblasts, indicating stage-specific expression.