Phosphodiesterase Activity of Alkaline Phosphatase in ATP-initiated Ca2+ 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-dayold chick embryos, under conditions where these both antagonistic and overlapping functions could be evidenced. Addition of 25 M 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.

Mechanism of Phosphorus Removal from Hanford Tank Sludge by Caustic Leaching

“…In contrast, the residual Ca solids displayed a very strong band at 1036 cm -1 , with surrounding weaker bands at 962 and 1093 cm -1 . The FTIR spectral pattern for the Ca residual was similar to that for hydroxyapatite itself and agrees with literature reports (Zhang et al 2005). The appearance of bands at 1417 and 1457 cm -1 in the FTIR spectrum of the Ca residual suggests that there might be some other, as yet identified, product present (these bands were not evident in the hydroxyapatite spectrum).…”

Structural and Functional Comparisons of Nucleotide Pyrophosphatase/Phosphodiesterase and Alkaline Phosphatase: Implications for Mechanism and Evolution,

“…NPP and AP are evolutionarily related members of the AP superfamily that have evolved to catalyze different reactions with remarkable specificity despite having very similar active sites. There are also members of the AP superfamily that appear to have nearly equivalent activities for phosphate monoester and diester hydrolysis (65). These enzymes may represent intermediate states along the evolutionary path from a specific phosphate monoesterase to a diesterase or vice versa.…”

Nicotinic Acid Adenine Dinucleotide Phosphate (NAADP) Degradation by Alkaline Phosphatase

“…Furthermore, the enzymatic characteristics observed in HeLa cells in our study indicated that PLAP is the most prominent isoform in these cells. Phosphodiesterase activity has been reported for TNAP, but not for PLAP (26,27). Importantly, in this study, phosphodiesterase activity using cAMP as substrate was not detected in HeLa cells (data not shown).…”