Reversibility of the reactions catalyzed by cholinephosphotransferase and ethanolaminephosphotransferase solubilized from rat-brain microsomes.
Biochim Biophys Acta
; 1165(2): 183-8, 1992 Dec 02.
Article
in En
| MEDLINE
| ID: mdl-1333282
ABSTRACT
The incorporation of CMP into CDP-ethanolamine and CDP-choline, catalyzed by ethanolaminephosphotransferase (EC 2.7.8.1) and cholinephosphotransferase (EC 2.7.8.2), respectively, has been studied in solubilized preparations of rat-brain microsomes. Mn2+ ions were required for the maximal activity of both enzymes. The CMP concentration needed to reach the half-maximal reaction rate was 1.6 microM for both activities. The rate of incorporation of CMP into CDP-choline and CDP-ethanolamine was increased by increasing the concentration of phosphatidylcholine and phosphatidylethanolamine, respectively, in detergent-phospholipid micellar systems. The rate of the reaction at pH 6.5 was comparable with that measured at pH 8.5, whereas the rate of synthesis of phosphatidylcholine and phosphatidylethanolamine, catalyzed by the same enzymes, increased with pH. Ethanolaminephosphotransferase, which catalyzes the synthesis of phosphatidylethanolamine from CDP-ethanolamine and diacylglycerol, was co-eluted with the enzyme activity catalyzing the reverse reaction, when solubilized microsomes were submitted to anion exchange chromatography on DEAE Bio-Gel A. Cholinephosphotransferase was inactivated during the chromatographic procedure.
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Collection:
01-internacional
Database:
MEDLINE
Main subject:
Brain
/
Diacylglycerol Cholinephosphotransferase
/
Ethanolaminephosphotransferase
/
Microsomes
Limits:
Animals
Language:
En
Journal:
Biochim Biophys Acta
Year:
1992
Document type:
Article
Affiliation country:
Italy