Purification and properties of galactokinase from pig liver |
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Authors: | F J Ballard |
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Institution: | Fels Research Institute, Temple University School of Medicine, Philadelphia, Pa. 19140, U.S.A. |
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Abstract: | 1. Galactokinase has been purified from the liver of young pigs by high-speed centrifugation, chromatography on Sephadex G-100 and DEAE-cellulose, and ammonium sulphate fractionation. 2. The enzyme preparation has a specific activity of 10-18mumoles of galactose phosphorylated/mg. of protein/min. at 37 degrees and has been purified 400-fold from the liver supernatant. 3. Purified liver galactokinase has Michaelis constants of 1x10(-4)-3x10(-4)m for galactose and 2x10(-4)m for ATP-Mg(2+), and the enzyme reaction produces equimolar amounts of galactose 1-phosphate and ADP. 4. Galactokinase phosphorylates 2-deoxygalactose and galactosamine in addition to galactose, has a pH optimum of 7.8, a Q(10) of 2, and is stimulated by cysteine and other thiols. 5. With the exception of substrate specificity, the properties of liver galactokinase are similar to galactokinase purified from yeast and Escherichia coli. |
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