Studies on avian erythrocyte metabolism: Purification and properties of myo-inositol 1-phosphatase from chick erythrocytes
| Autor: | R.E. Isaacks, S. Roth, Donald R. Harkness |
|---|---|
| Rok vydání: | 1981 |
| Předmět: |
Erythrocytes
Pyrimidine Cations Divalent Inositol Phosphates Phosphatase Biophysics Biology Biochemistry Substrate Specificity Divalent chemistry.chemical_compound Drug Stability Animals Inositol Molecular Biology chemistry.chemical_classification Hydrogen-Ion Concentration Phosphate Molecular biology Phosphoric Monoester Hydrolases Yeast Enzyme assay Molecular Weight Kinetics Enzyme chemistry biology.protein Chickens |
| Zdroj: | Archives of Biochemistry and Biophysics. 210:465-473 |
| ISSN: | 0003-9861 |
| Popis: | An enzyme capable of hydrolyzing myo -inositol 1-phosphate was identified and partially purified from the erythrocytes of 7-day chicks. It has an apparent molecular weight of approximately 60,000, is heat stable, and has a pH of optimal activity between 6.5 and 7.3. In most regards the kinetic properties are similar to the myo -inositol 1-phosphatases of rat testis, rat mammary gland, bovine brain, and of yeast. The enzyme has an absolute requirement for a divalent cation; Mg 2+ gave the greatest activity, with an optimal concentration of 2.5 m m in the standard assay employed. Zn 2+ , Co 2+ , and Mn 2+ supported activity to a lesser degree. Activity was inhibited by NaF, HgCl 2 , and p -hydroxymercuribenzoate. myo -Inositol tetrakis (dihydrogen phosphate) and myo -inositol 1,3,4,5,6-pentakis (dihydrogen phosphate) were not substrates for this enzyme and inhibited the hydrolysis of myo -inositol 1-phosphate. Unlike other phosphatases for myo -inositol 1-phosphate, this enzyme cleaved myo -inositol 1-phosphate ( K m = 8.6 × 10 −5 m) and myo -inositol 2-phosphate ( K m = 2.86 × 10 −4 m) at approximately the same rates. It also hydrolyzed 2′-purine and pyrimidine ribonucleotides about as well as myo -inositol 1-phosphate, but was only 20–30% as active against the 3′-ribonucleotides and had scarcely any activity against the 5′-ribonucleotides. The amount of enzyme activity in erythrocytes of embryos, chicks, and mature chickens was the same (~29 μmol/ml rbc/h). The biological function of this enzyme in avian erythrocytes is unclear at this time. Other tissues containing this phosphatase also have an enzyme which synthesizes myo -inositol 1-phosphate from glucose 6-phosphate, but we have been unable to detect the presence of such an enzyme in avian erythrocytes. |
| Databáze: | OpenAIRE |
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