An enzyme with an
alkaline pH optimum that hydrolyzes phosphate monoesters.
Elevation of its activity in the serum usually indicates obstructive
jaundice, Paget’s disease (osteitis deformans), or bone
carcinoma.
Alkaline Phosphatase is commonly used to remove the 5′-terminal phosphate from nucleic acids.
일반 설명
Alkaline phosphatase from bovine intestinal mucosa is both a phosphomonoesterase and a pyrophosphatase.
Purification Methods
The E.coli supernatant in sucrose (20%, 33mM) in Tris-HCl pH 8.0 is purified through a DEAE-cellulose column and recrystallised. To the column eluates in 0.125M NaCl is added MgCl2 (to 0.01M) and brought to 50% saturation in (NH4)2SO4 by adding the solid (0.20g/mL). The mixture is centrifuged to remove bubbles and is adjusted to pH 8.0 (with 2N NaOH). Saturated (NH4)2SO4 at pH 8.0 is added dropwise until the solution becomes faintly turbid (~61% saturation). It is set aside at ~25o for 1hour (turbidity will increase). The mixture is placed in an ice bath for several minutes when turbidity disappears and a clear solution is obtained. It is then placed in a large ice bath at 0o (~5L) and allowed to warm slowly to room temperature in a dark room whereby crystals are formed appearing as a silky sheen. The crystals are collected by centrifugation at 25o if necessary. The crystalline solutions are stable at ~25o for many months. They can be stored at 0o, but are unstable when frozen. Cysteine at 10-3M and thioglycolic acid at 10-4M are inhibitory. This is reversed on addition of Zn2+ ions. Many organic phosphates are good substrates for this phosphatase. [Molamy & Horecker Methods Enzymol 9 639 1966, Torriani et al. Methods Enzymol 12b 212 1968, Engstrom Biochim Biophys Acta 92 71 1964.] Alkaline phosphatase from rat osteosarcoma has been purified by Me2CO precipitation and chromatography on DEAE-cellulose, Sephacryl S-200, and hydroxylapatite. [Nair et al. Arch Biochem Biophys 254 18 1987.] Phosphoproteins (various). These are purified by adsorbing onto an iminodiacetic acid substituted agarose column to which are bound ferric ions. This chelate complex acts as a selective immobilised metal affinity adsorbent for phosphoproteins. [Muszyfiska et al. Biochemistry 25 6850 1986.]
