PHD2 also known as HIFPHD2, EGLN1 functions as a prolyl hydroxylase, catalyzing post-translational modification of hypoxia-inducible factor (HIF) alpha subunits, which regulates gene expression in response to oxygen levels. This modification determines HIF-α protein stability and activity, influencing cellular responses to hypoxia. PHD2′s ability to hydroxylate HIF-α subunits enables cellular adaptation to varying oxygen conditions, making PHD2 essential for angiogenesis, metabolism, and cell survival. PHD2′s role in stabilizing HIF-1α under normoxic conditions maintains cellular function and environmental response capabilities. PDH2 catalyzes the post-translational formation of 4-hydroxyproline in hypoxia-inducible factor (HIF) alpha proteins. HIF is a transcriptional complex that plays a central role in mammalian oxygen homeostasis.