ISSN:
1471-4159
Quelle:
Blackwell Publishing Journal Backfiles 1879-2005
Thema:
Medizin
Notizen:
A prominent galactose-1-phosphatase was isolated from rat brain and partially purified by chromatography on diethylaminoethyl-Sephacel, hydroxylapatite, and Sephacryl S-300 columns. The galactose-1-phosphatase was separated from alkaline phosphatase, and from two forms of glucose-1-phosphatase. The three columns gave a 10-fold increase in specific activity to 290 mol/min/mg of protein, with a yield of 15%. Of the eight sugar phosphates tested, galactose-1-phosphate was the best substrate for the purified enzyme, followed by glucose-1-phosphate, which was hydrolyzed 40% as rapidly as galactose-1-phosphate. Galactose-1-phosphatase had an optimum pH of 8.5 and a Km value of 2.5 mM for galactose-1-phosphate hydrolysis. Mg2+ was required for activity, and supported half-maximal activity at a concentration of 1.25 mM. Phosphate was the only potent inhibitor found. ATP, arsenate, and vanadate caused moderate inhibition of 10 mM levels, whereas AMP, L-homoarginine, and L-phenylalanine stimulated enzyme activity. Galactose-1-phosphatase was determined to have a Stokes radius of 30 A and a sedimentation coefficient of 4.IS. These values were used to calculate a molecular weight of 50,200 and a factional ratio showing the enzyme to be a globular protein. It is hypothesized that a similar phosphatase may play a role in reducing brain galactose-1 -phosphate concentrations in patients with galactosemia.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1111/j.1471-4159.1991.tb03781.x
Permalink
