Bone Abstracts

Bone cells control initial steps of mineralization by forming matrix vesicles (MVs) in which calcium and phosphate ions are accumulated. Under physiological conditions, MVs are released to the extracellular matrix (ECM) and Ca2+ and Pi form hydroxyapatite (HA). Growing minerals break the MVs membrane and are deposited in ECM. Under pathological conditions the mineralization process becomes deregulated, which leads to the formation of calcium phosphate deposits. It is suggested...

Bone mineralization is initiated by matrix vesicles (MVs), cell-derived structures released into the extracellular matrix which are nucleation sites for hydroxyapatite (HA) formation. It is suggested that annexins are mineralization-stimulating membrane proteins that exhibit ion channel activity and facilitate the influx of Ca2+ into MVs. The process is also regulated via enzymatic degradation of inhibitory pyrophosphate by tissue-nonspecific alkaline phosphatase (T...

Up to now, most of standard methods for measuring inorganic phosphate (Pi) to determine phosphatase activity are based on coupled enzyme assays, colorimetric methods or conductance measurements. However, none of these methods can measure Pi, substrate and protein concentrations simultaneously, allowing direct kinetic determinations of phosphatase activity in cells in a single assay. Among the enzymes having a pyrophosphatase activity and releasing Pi...