title: Phosphodiesterase activity of alkaline phosphatase in ATP-initiated Ca(2+) and phosphate deposition in isolated chicken matrix vesicles.
abstract: Inorganic pyrophosphate is a potent inhibitor of bone mineralization by preventing the seeding of calcium-phosphate complexes. Plasma cell membrane glycoprotein-1 and tissue nonspecific alkaline phosphatase were reported to be antagonistic regulators of mineralization toward inorganic pyrophosphate formation (by plasma cell membrane glycoprotein-1) and degradation (by tissue nonspecific alkaline phosphatase) under physiological conditions. In addition, they possess broad overlapping enzymatic functions. Therefore, we examined the roles of tissue nonspecific alkaline phosphatase within matrix vesicles isolated from femurs of 17-day-old chick embryos, under conditions where these both antagonistic and overlapping functions could be evidenced. Addition of 25 microM ATP significantly increased duration of mineralization process mediated by matrix vesicles, while supplementation of mineralization medium with levamisole, an alkaline phosphatase inhibitor, reduces the ATP-induced retardation of mineral formation. Phosphodiesterase activity of tissue nonspecific alkaline phosphatase for bis-p-nitrophenyl phosphate was confirmed, the rate of this phosphodiesterase activity is in the same range as that of phosphomonoesterase activity for p-nitrophenyl phosphate under physiological pH. In addition, tissue nonspecific alkaline phosphatase at pH 7.4 can hydrolyze ADPR. On the basis of these observations, it can be concluded that tissue nonspecific alkaline phosphatase, acting as a phosphomonoesterase, could hydrolyze free phosphate esters such as pyrophosphate and ATP, while as phosphodiesterase could contribute, together with plasma cell membrane glycoprotein-1, in the production of pyrophosphate from ATP.
authors.affiliation: Laboratoire de Physico-Chimie Biologique, UMR CNRS 5013, Université Claude Bernard Lyon 1, UFR de Chimie-Biochimie F-69622 Villeurbanne, France. le_zhang@hotmail.com
authors.forename: Le
authors.initials: L
authors.lastname: Zhang
authors.forename: Marcin
authors.initials: M
authors.lastname: Balcerzak
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Radisson
authors.forename: Cyril
authors.initials: C
authors.lastname: Thouverey
authors.forename: Slawomir
authors.initials: S
authors.lastname: Pikula
authors.forename: Gérard
authors.initials: G
authors.lastname: Azzar
authors.forename: René
authors.initials: R
authors.lastname: Buchet
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000469:Alkaline Phosphatase / Q000378:metabolism*; D000818:Animals; D001857:Bone Matrix / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D002113:Calcification, Physiologic / Q000502:physiology*; D002352:Carrier Proteins / Q000378:metabolism; D002642:Chick Embryo; D009596:Nitrophenols / Q000378:metabolism; D009943:Organophosphorus Compounds / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism*; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D011755:Pyrophosphatases / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D009596:Nitrophenols; D009943:Organophosphorus Compounds; D010710:Phosphates; C008644:nitrophenylphosphate; D000255:Adenosine Triphosphate; D000469:Alkaline Phosphatase; D010727:Phosphoric Diester Hydrolases; C065962:ectonucleotide pyrophosphatase phosphodiesterase 1; D011755:Pyrophosphatases