Analysis of recombinant Phex: an endopeptidase in search of a substrate.

Journal Article (Journal Article)

X-linked hypophosphatemia (XLH) is caused by inactivating mutations of Phex, a phosphate-regulating endopeptidase. Further advances in our knowledge of the pathogenesis of XLH require identification of the biological function of Phex and its physiologically relevant substrates. We evaluated several potential substrates using mouse recombinant wild-type Phex proteins (rPhex-WT) and inactive mutant Phex proteins (rPhex-3'M) lacking the COOH-terminal catalytic domain as controls. By Western blot analysis, we demonstrated that Phex is a membrane-bound 100-kDa glycosylated monomer. Neither casein, a substrate for the related endopeptidase thermolysin, human stanniocalcin 1 (hSTC-1), an osteoblast-derived phosphate-regulating factor, nor FGF-23 peptide (amino acid 172-186), comprising the region mutated in autosomal dominant hypophosphatemia, was cleaved by rPhex-WT. In addition, membranes expressing rPhex-WT, rPhex-3'M, and the empty vector hydrolyzed parathyroid hormone-(1-34), indicating the lack of Phex-specific cleavage of parathyroid hormone. In contrast, rPhex-WT did display an EDTA-dependent cleavage of the neutral endopeptidase substrate [Leu]enkephalin. Further studies with wild-type and mutant rPhex proteins should permit the identification of physiologically relevant substrates involved in the pathogenesis of XLH.

Full Text

Duke Authors

Cited Authors

  • Guo, R; Liu, S; Spurney, RF; Quarles, LD

Published Date

  • October 1, 2001

Published In

Volume / Issue

  • 281 / 4

Start / End Page

  • E837 - E847

PubMed ID

  • 11551862

International Standard Serial Number (ISSN)

  • 0193-1849

Digital Object Identifier (DOI)

  • 10.1152/ajpendo.2001.281.4.E837


  • eng

Conference Location

  • United States