Acid nucleoside triphosphatase: partial purification and characterization of a new enzyme from human serum.
Acid nucleoside triphosphatase (Acid NTPase), an enzyme which catalyzes the hydrolysis of all nucleoside triphosphates to the corresponding diphosphates was purified from human serum with a purification factor of 190 and a recovery of 31%. The molecular weight was 75,000 as estimated by gel filtration. Gel-electrophoresis revealed an Rf-value of 0.11, and the isoelectric point was determined at pH 4.4. It exhibited a temperature optimum of 44 degrees C and the activation energy was estimated to be 41.6 kJ/mol. The enzyme was active in the absence of divalent cations, since activity was not inhibited by EDTA. The presence of this chelator reduced the Km-value from 70 to 40 microM. Inhibitor experiments revealed that tartrate was a weak mixed-type noncompetitive inhibitor, Ki = 88 mM. The enzyme was specific for the hydrolysis of nucleoside triphosphates. P-nitrophenyl phosphate was not accepted as a substrate. The enzyme revealed optimum activity at the exceptionally acid pH of 3.0. These unique characteristics indicate the presence of a novel enzyme.
Dahlmann
N
N
Institut für Klinische Biochemie, Bonn, FRG.
Kirchgesser
M
M
D002412:Cations / Q000494:pharmacology; D002614:Chelating Agents / Q000494:pharmacology; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D004492:Edetic Acid / Q000494:pharmacology; D005590:Fractional Precipitation; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007525:Isoelectric Focusing; D008970:Molecular Weight; D043583:Nucleoside-Triphosphatase; D009711:Nucleotides / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000097:blood* / Q000302:isolation & purification / Q000378:metabolism; D013379:Substrate Specificity; D013696:Temperature
D002412:Cations; D002614:Chelating Agents; D009711:Nucleotides; D004492:Edetic Acid; D010744:Phosphoric Monoester Hydrolases; D043583:Nucleoside-Triphosphatase