PH4 (Transmembrane Prolyl 4-hydroxylase, P4H-TM, Hypoxia-inducible Factor Prolyl Hydroxylase 4, HIF-PH4, HIF-prolyl Hydroxylase 4, HPH-4, P4HTM, PH-4)

Antibodies / Antibodies-Hypoxia

-20°C

Supplied as a lyophilized powder from PBS, 0.05% sodium azide.

Synthetic peptide corresponding to 17aa of human PH-4, C-terminal.

Oxygen is absolutely critical for the survival of mammalian cells. Hypoxia induced factor (HIF) is a transcriptional complex that plays a central role in mammalian oxygen homeostasis. There are 3-types of alpha subunits (HIF1-3alpha) and one HIF-beta subunits. However, the three HIF-alpha subunits are regulated by oxygen in a similar fashion, i.e. by regulated stabilization of the alpha-subunits. Under normal conditions, HIF-alpha Prolines are hydroxylated at Pro-402 and Pro-564. This allows binding of von Hippel-Lindau (VHL), the substrate recognition component of the E3 ubiquinated ligase complex, subsequent ubiquitination and degradation of HIF-alpha by the proteasome. Under hypoxic conditions, hydroxylation of HIF-alpha is inhibited and this prevents HIF-alpha degradation. The enzymes responsible for HIF-hydroxylation are known as HIF-prolyl hydroxylases (PHD1- 3 or HPH1, HPH2, and HPH3). The three PHDs have been identified to hydroxylate the motif, LXXLAP* with *P being the hydroxyproline.

A novel putative proline hydroxylase, PH-4, with an N-terminal EF-hand motif and a C-terminal catalytic domain with 1 transmembrane domain has been identified in endoplasmic reticulum. PH-4 showed approx. 10-15% homology with the collagen prolyl 4-hydroxylases, PH-alpha I, and PH-alpha II. Human PH-4 (502aa, chromosome 3pp21.3) is highly expressed in most tissues. Like PHD1-3, PH-4 suppressed the HIF transactivation activity, dependent on the consensus oxygen-dependent degradation domain (ODDD) proline residues. Ph-4 levels correlated with the cellular HIF concentration. Therefore, PH-4 may also be involved in cellular oxygen sensing mechanism.

Applications:
Suitable for use in Western Blot and ELISA. Other applications not tested.

Recommended Dilution:
Western Blot: 1-5ug/ml (chemiluminescence)
ELISA: 1:10, 000-1:100, 000; 50-100ng control peptide/well
Optimal dilutions to be determined by the researcher.

Storage and Stability:
Lyophilized powder may be stored at -20°C. Stable for 12 months at -20°C. Reconstitute with sterile ddH2O or PBS. Aliquot to avoid repeated freezing and thawing. Store at -20°C. Reconstituted product is stable for 12 months at -20°C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer.