Biomaterial Database

The phosphatidylinositol-glycolipid anchor on alkaline phosphatase facilitates mineralization initiation in vitro. 1995

G Harrison, and I M Shapiro, and E E Golub

Department of Biochemitry, University of Pennsylvania School of Dental Medicine, Philadelphia, USA.

Alkaline phosphatase (AP) is required for the proper mineralization of cartilage and bone. The enzyme is localized to the outer surface of cells through a phosphatidylinositol-glycolipid anchor, which is covalently attached to the carboxyl terminus of the protein. In calcifying cartilage, AP-rich matrix vesicles (MVs) are released into the matrix from chondrocytes, and apatite formation is initiated within and around these particles. In this paper we examine the role of the AP glycolipid anchor using an in vitro mineralization assay system. AP was purified to homogeneity, and the purified enzyme was used to drive mineral formation in vitro with and without the anchor. Mineral formation was initiated through phosphate release from beta-glycerol phosphate (beta-GP). The amount of PO4(-3) released was similar whether the anchor was present or absent. However, SEM and X-ray microanalysis revealed that the mineral produced by anchored AP was indistinguishable from that produced by MVs and that both of those minerals were more apatite-like than mineral formed by soluble AP or through spontaneous precipitation. Taken together, the data suggest that in addition to providing PO4(-3) to drive mineralization, AP influences the nature of the mineral formed. Further, AP containing its glycolipid anchor produces mineral comparable with that formed by tissue-derived MVs. Thus, in the absence of extracellular matrix, MV mineralization in vitro can be emulated by glycolipid-anchor containing AP.

UI	MeSH Term	Description	Entries
D008855	Microscopy, Electron, Scanning	Microscopy in which the object is examined directly by an electron beam scanning the specimen point-by-point. The image is constructed by detecting the products of specimen interactions that are projected above the plane of the sample, such as backscattered electrons. Although SCANNING TRANSMISSION ELECTRON MICROSCOPY also scans the specimen point by point with the electron beam, the image is constructed by detecting the electrons, or their interaction products that are transmitted through the sample plane, so that is a form of TRANSMISSION ELECTRON MICROSCOPY.	Scanning Electron Microscopy,Electron Scanning Microscopy,Electron Microscopies, Scanning,Electron Microscopy, Scanning,Electron Scanning Microscopies,Microscopies, Electron Scanning,Microscopies, Scanning Electron,Microscopy, Electron Scanning,Microscopy, Scanning Electron,Scanning Electron Microscopies,Scanning Microscopies, Electron,Scanning Microscopy, Electron
D008970	Molecular Weight	The sum of the weight of all the atoms in a molecule.	Molecular Weights,Weight, Molecular,Weights, Molecular
D010710	Phosphates	Inorganic salts of phosphoric acid.	Inorganic Phosphate,Phosphates, Inorganic,Inorganic Phosphates,Orthophosphate,Phosphate,Phosphate, Inorganic
D010727	Phosphoric Diester Hydrolases	A class of enzymes that catalyze the hydrolysis of one of the two ester bonds in a phosphodiester compound. EC 3.1.4.	Phosphodiesterase,Phosphodiesterases,Hydrolases, Phosphoric Diester
D012015	Reference Standards	A basis of value established for the measure of quantity, weight, extent or quality, e.g. weight standards, standard solutions, methods, techniques, and procedures used in diagnosis and therapy.	Standard Preparations,Standards, Reference,Preparations, Standard,Standardization,Standards,Preparation, Standard,Reference Standard,Standard Preparation,Standard, Reference
D002113	Calcification, Physiologic	Process by which organic tissue becomes hardened by the physiologic deposit of calcium salts.	Bone Mineralization,Calcification, Physiological,Physiologic Calcification,Mineralization, Bone,Physiological Calcification
D002645	Chickens	Common name for the species Gallus gallus, the domestic fowl, in the family Phasianidae, order GALLIFORMES. It is descended from the red jungle fowl of SOUTHEAST ASIA.	Gallus gallus,Gallus domesticus,Gallus gallus domesticus,Chicken
D004577	Electron Probe Microanalysis	Identification and measurement of ELEMENTS and their location based on the fact that X-RAYS emitted by an element excited by an electron beam have a wavelength characteristic of that element and an intensity related to its concentration. It is performed with an electron microscope fitted with an x-ray spectrometer, in scanning or transmission mode.	Microscopy, Electron, X-Ray Microanalysis,Spectrometry, X-Ray Emission, Electron Microscopic,Spectrometry, X-Ray Emission, Electron Probe,X-Ray Emission Spectrometry, Electron Microscopic,X-Ray Emission Spectrometry, Electron Probe,X-Ray Microanalysis, Electron Microscopic,X-Ray Microanalysis, Electron Probe,Microanalysis, Electron Probe,Spectrometry, X Ray Emission, Electron Microscopic,Spectrometry, X Ray Emission, Electron Probe,X Ray Emission Spectrometry, Electron Microscopic,X Ray Emission Spectrometry, Electron Probe,X-Ray Microanalysis,Electron Probe Microanalyses,Microanalyses, Electron Probe,Microanalysis, X-Ray,Probe Microanalyses, Electron,Probe Microanalysis, Electron,X Ray Microanalysis,X Ray Microanalysis, Electron Microscopic,X Ray Microanalysis, Electron Probe
D004591	Electrophoresis, Polyacrylamide Gel	Electrophoresis in which a polyacrylamide gel is used as the diffusion medium.	Polyacrylamide Gel Electrophoresis,SDS-PAGE,Sodium Dodecyl Sulfate-PAGE,Gel Electrophoresis, Polyacrylamide,SDS PAGE,Sodium Dodecyl Sulfate PAGE,Sodium Dodecyl Sulfate-PAGEs
D005994	Glycerophosphates	Any salt or ester of glycerophosphoric acid.	Glycerolphosphate,Glycerophosphate,Calcium Glycerophosphate,Glycerolphosphates,Glycerophosphate, Calcium