title: Solubility properties of alkaline phosphatase from matrix vesicles.
abstract: Alkaline phosphatase has been extracted from matrix vesicles of a calcifying cartilage with 0.15 M KCl, 0.4 M guanidinium chloride and 0.05 M deoxycholate/50% butanol mixture. The catalytic properties of the three extracts have been compared. Although the highest amount of enzyme activity is extracted with the latter reagent (55%), some of it is also extracted with KCl (11%) and guanidinium (7%). By submitting isolated matrix vesicles to a short time sonication the distribution pattern of the alkaline phosphatase activity in the extracts is clearly modified, as the amount extracted with KCl increases from 14 to 50% and the portion extracted with deoxycholate decreases from 55 to 27% of the total enzyme activity of matrix vesicles. The enzymatic preparations were comparable on the basis of specific activities, affinity for the substrates (p-nitrophenylphosphate, ATP), thermostability, sensitivity to inhibitors and activators. By electrofocusing a value of pI = 4.15 was found for the alkaline phosphatase of matrix vesicles independently of the extraction medium. These results contradict the concept that alkaline phosphatase is exclusively an intrinsic membrane protein.
mesh_terms: D009597:4-Nitrophenylphosphatase / Q000302:isolation & purification / Q000378:metabolism; D000469:Alkaline Phosphatase / Q000302:isolation & purification / Q000378:metabolism*; D000818:Animals; D000440:Butanols; D002118:Calcium / Q000494:pharmacology; D002356:Cartilage / Q000201:enzymology*; D002417:Cattle; D003840:Deoxycholic Acid; D019791:Guanidine; D006146:Guanidines; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D012540:Scapula; D012995:Solubility
chemical_list: D000440:Butanols; D006146:Guanidines; D003840:Deoxycholic Acid; D000469:Alkaline Phosphatase; D009597:4-Nitrophenylphosphatase; D008274:Magnesium; D019791:Guanidine; D002118:Calcium