@article {38143,
	title = {Carbonic anhydrase III: the phosphatase activity is extrinsic},
	journal = {Archives of biochemistry and biophysicsArchives of biochemistry and biophysics},
	volume = {377},
	year = {2000},
	note = {http://www.ncbi.nlm.nih.gov/pubmed/10845711?dopt=Abstract},
	type = {10.1006/abbi.2000.1793},
	abstract = {The carbonic anhydrases reversibly hydrate carbon dioxide to yield bicarbonate and hydrogen ion. They have a variety of physiological functions, although the specific roles of each of the 10 known isozymes are unclear. Carbonic anhydrase isozyme III is particularly rich in skeletal muscle and adipocytes, and it is unique among the isozymes in also exhibiting phosphatase activity. Previously published studies provided evidence that the phosphatase activity was intrinsic to carbonic anhydrase III, that it had specificity for tyrosine phosphate, and that activity was regulated by reversible glutathionylation of cysteine186. To study the mechanism of this phosphatase, we cloned and expressed the rat liver carbonic anhydrase III. The purified recombinant had the same specific activity as the carbonic anhydrase purified from rat liver, but it had virtually no phosphatase activity. We attempted to identify an activator of the phosphatase in rat liver and found a protein of approximately 14 kDa, the amount of which correlated with the phosphatase activity of the carbonic anhydrase III fractions. It was identified as liver fatty acid binding protein, which was then purified to test for activity as an activator of the phosphatase and for protein-protein interaction, but neither binding nor activation could be demonstrated. Immunoprecipitation experiments established that carbonic anhydrase III could be separated from the phosphatase activity. Finally, adding additional purification steps completely separated the phosphatase activity from the carbonic anhydrase activity. We conclude that the phosphatase activity previously considered to be intrinsic to carbonic anhydrase III is actually extrinsic. Thus, this isozyme exhibits only the carbon dioxide hydratase and esterase activities characteristic of the other mammalian isozymes, and the phosphatase previously shown to be activated by glutathionylation is not carbonic anhydrase III.},
	keywords = {Animals, Carbonic Anhydrases, Chromatography, High Pressure Liquid, Cloning, Molecular, Enzyme Activation, Glutathione, Kinetics, Liver, Male, Muscles, Phosphoric Monoester Hydrolases, Precipitin Tests, Rabbits, Rats, Rats, Inbred F344, Recombinant Proteins, Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization, Time factors},
	author = {Kim, G. and J. Selengut and Levine, R. L.}
}
@article {38369,
	title = {MDP-1: A novel eukaryotic magnesium-dependent phosphatase},
	journal = {BiochemistryBiochemistry},
	volume = {39},
	year = {2000},
	note = {http://www.ncbi.nlm.nih.gov/pubmed/10889041?dopt=Abstract},
	abstract = {We report here the purification, cloning, expression, and characterization of a novel phosphatase, MDP-1. In the course of investigating the reported acid phosphatase activity of carbonic anhydrase III preparations, several discrete phosphatases were discerned. One of these, a magnesium-dependent species of 18.6 kDa, was purified to homogeneity and yielded several peptide sequences from which the parent gene was identified by database searching. Although orthologous genes were identified in fungi and plants as well as mammalian species, there was no apparent homology to any known family of phosphatases. The enzyme was expressed in Escherichia coli with a fusion tag and purified by affinity methods. The recombinant enzyme showed magnesium-dependent acid phosphatase activity comparable to the originally isolated rabbit protein. The enzyme catalyzes the rapid hydrolysis of p-nitrophenyl phosphate, ribose-5-phosphate, and phosphotyrosine. The selectivity for phosphotyrosine over phosphoserine or phosphothreonine is considerable, but the enzyme did not show activity toward five phosphotyrosine-containing peptides. None of the various substrates assayed (including various nucleotide, sugar, amino acid and peptide phosphates, phosphoinositides, and phosphodiesters) exhibited K(M) values lower than 1 mM, and many showed negligible rates of hydrolysis. The enzyme is inhibited by vanadate and fluoride but not by azide, cyanide, calcium, lithium, or tartaric acid. Chemical labeling, refolding, dialysis, and mutagenesis experiments suggest that the enzymatic mechanism is not dependent on cysteine, histidine, or nonmagnesium metal ions. In recognition of these observations, the enzyme has been given the name magnesium-dependent phosphatase-1 (MDP-1).},
	keywords = {Amino Acid Sequence, Animals, Catalysis, Cations, Chromatography, Affinity, Cloning, Molecular, Cysteine, Enzyme Inhibitors, Histidine, Hydrogen-Ion Concentration, Magnesium, Mice, Molecular Sequence Data, Phosphoprotein Phosphatases, Protein Phosphatase 1, Rabbits, Sequence Analysis, Protein, Sequence Homology, Amino Acid, Substrate Specificity},
	author = {J. Selengut and Levine, R. L.}
}
