Prolyl hydroxylase domain-containing protein 1; Prolyl hydroxylase domain-containing protein 2 (PHD1; PHD2)

Prolyl hydroxylase domain-containing proteins 1 and 2 (PHD1 and PHD2) are essential enzymes in human oxygen homeostasis. These proteins function by hydroxylating specific proline residues within HIF-α subunits under normoxic conditions, enabling recognition by the von Hippel-Lindau (VHL) E3 ubiquitin ligase complex, which marks HIF-α for proteasomal degradation[1][2][3][5]. This mechanism ensures that, in low oxygen environments, HIF-α escapes degradation, translocates to the nucleus, and activates transcription of genes that facilitate adaptation to hypoxia (including those involved in angiogenesis, erythropoiesis, and metabolism)[5][6]. PHD2 is considered the main cellular oxygen sensor and is the most abundant isoform in most cell types, with knockout resulting in embryonic lethality in mice[3][4][6]. Pharmacological inhibition of PHDs is being explored for diseases where enhanced hypoxic responses are beneficial, including anemia and ischemic conditions[7]. Safety concerns for targeting these enzymes arise mainly from potential cancer-promoting effects and off-target gene activation due to widespread HIF stabilization.

Other names

EGLN2HPH3HIF-PH1EGLN1HPH2Egl nine homolog 1HIF-PH2

Inhibition of PHDs prevents prolyl hydroxylation of HIF-α, leading to HIF stabilization, increased HIF activity, and enhanced expression of hypoxia-responsive genes