Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.24.11 (CD10)
 9,792 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Renal proximal tubular reabsorption of phosphate and intestinal absorption both regulate phosphate homeostasis. Brush-border membrane Npt2a cotransporter is the key element in proximal tubular P (i) reabsorption. Inactivating mutations of Npt2a cause bone demineralisation and urolithiasis. An excess of a phosphaturic factor, called "Phosphatonin", could modulate phosphate reabsorption by inhibition on Npt2a. Inactivating mutation of PHEX, an endopeptidase-membrane coding gene, is responsible for X-linked Hypophosphatemia (XLH), because of an impaired degradation of phosphatonine by PHEX product. Autosomic Dominant Hypophosphatemic Rickets (ADHR) is explained by a mutation preventing FGF23 (one of the best identified phosphatonines) from cleavage. According recent data, FGF23, MEPE (Matrix Extracellular Phosphoglycoprotein) et FRP4 (frizzled related protein-4) are 3 putative "phosphatonines".
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PMID:[Genetic hypophosphatemia: recent advances in physiopathogenic concept]. 1595 11

Bone is mineralized when hydroxyapatite crystals derived from calcium ions and inorganic phosphate (Pi) grow along collagen fibrils in the extracellular matrix. Mineralization is initiated by nucleation of those crystals. Mature osteoblasts secrete matrix vesicles into osteoid, which contain growing hydroxyapatite crystal seeds. After rupture of the lipid bilayer of those vesicles, crystals continue to grow as a mineralized nodule and adhere to collagen fibrils. It remains controversial whether nucleation occurs mainly in matrix vesicles or also extra-vesicularly around collagen fibrils. Mineralization is inhibited by pyrophosphate (PPi) and by SIBLING family proteins, which carry an acidic serine- and aspartate-rich motif (ASARM) and include osteopontin, dentin matrix protein 1 and MEPE. Intracellular and extracellular activity of these factors is regulated by the PPi-generating ectonucleotide pyrophosphatase/phosphodiesterase (ENPP1) , the PPi-transporter progressive ankylosis (ANK) protein, the PPi-degrading/Pi-generating ectoenzyme alkaline phosphatase (ALPL, TNAP) , and PHEX endopeptidase. Gain- or loss-of-function mutations in genes encoding these proteins are associated with mineralization disorders such as ectopic calcification and other pathologies.
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PMID:[Updates on rickets and osteomalacia: mechanism and regulation of bone mineralization]. 2407 44

The proteolytic fragment ASARM (acidic serine- and aspartate-rich motif) of MEPE (matrix extracellular phosphoglycoprotein) (MEPE-ASARM) may act as an endogenous anti-mineralization factor involved in X-linked hypophosphatemic rickets/osteomalacia (XLH). We synthesized MEPE-ASARM peptides and relevant peptide fragments with or without phosphorylated Ser residues (pSer) to determine the active site(s) of MEPE-ASARM in a rat calvaria cell culture model. None of the synthetic peptides elicited changes in cell death, proliferation or differentiation, but the peptide (pASARM) with three pSer residues inhibited mineralization without causing changes in gene expression of osteoblast markers tested. The anti-mineralization effect was maintained in peptides in which any one of three pSer residues was deleted. Polyclonal antibodies recognizing pASARM but not ASARM abolished the pASARM effect. Deletion of six N-terminal residues but leaving the recognition sites for PHEX (phosphate regulating endopeptidase homolog, X-linked), a membrane endopeptidase responsible for XLH, intact and two C-terminal amino acid residues did not alter the anti-mineralization activity of pASARM. Our results strengthen understanding of the active sites of MEPE-pASARM and allowed us to identify a shorter more stable sequence with fewer pSer residues still exhibiting hypomineralization activity, reducing peptide synthesis cost and increasing reliability for exploring biological and potential therapeutic effects.
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PMID:Active sites of human MEPE-ASARM regulating bone matrix mineralization. 3271 87