[PROPERTIES OF CHICKEN LIVER MEMBRANE-ASSOCIATED THIAMINE TRIPHOSPHATASE]
| Autor: | Makarchikov Af, Kolas Ik |
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| Rok vydání: | 2015 |
| Předmět: |
Anions
Cations Divalent ATPase Phosphatase Thiamin-Triphosphatase Biochemistry Thiamine Triphosphate localization Substrate Specificity lcsh:Biochemistry Hydrolysis chemistry.chemical_compound kinetic properties Thiamine triphosphatase chicken liver Animals lcsh:QD415-436 chemistry.chemical_classification biology Cell Membrane Metabolism Hydrogen-Ion Concentration Enzyme chemistry Liver Solubility biology.protein thiamine triphosphatase Thiamine triphosphate Chickens solubilization |
| Zdroj: | Ukrainian Biochemical Journal, Vol 87, Iss 3, Pp 37-46 (2015) |
| ISSN: | 2409-4943 |
| Popis: | The enzymes involved in thiamine triphosphate (ThTP) metabolism in birds are not characterized so far. The aim of the present work was to study some properties of ThTPase in chicken liver. In liver homogenate, ThTPase activity has been found to display a bell-like pH-profile with a maximum of 5.5-6.0. Low activity was observed without divalent metal ions, while the addition of Mg2+ or Ca2+, each at 5 mM concentration, enhanced the rate of ThTP hydrolysis by a factor of 17-20. In the presence of 5 mM Mg2+ an apparent K(m) of the enzyme for ThTP was estimated by the method of non-linear regression as well as from the Hanes plot to be 1.7-2.2 mM. Monovalent anions such as I-, SCN-, NO3-, Br-, Cl- (at 150 mM concentration) showed inhibitory effect decreasing the rate of ThTPase reaction by 20-60%. After the homogenate was centrifuged, more than 85% of ThTPase activity was revealed in the fraction of insoluble particles indicating a membrane localization of the enzyme. The precipitate treatment with 1% sodium deoxycholate caused about 53% solubilization of the activity. During Toyopeal HW-55 chromatography, ThTPase activity was eluted simultaneously with ATPase and ITPase peaks in the void volume of the column. Thus, a non-specific high molecular mass protein complex seems to be involved in ThTP hydrolysis in the chicken liver. The chicken liver phosphatase is clearly distinguishable from all membrane-bound ThTPases reported previously. |
| Databáze: | OpenAIRE |
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