J. Lipid Res.
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A more recent version of this article appeared on October 1, 2007

Papers In Press, published online ahead of print July 23, 2007
J. Lipid Res., doi:10.1194/jlr.M600536-JLR200
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Submitted on December 19, 2006
Revised on July 6, 2007
Accepted on July 23, 2007

Alternative splicing of CTP: Phosphoethanolamine cytidylyltransferase produces two isoforms that differ in catalytic properties

Angela Tie and Marica Bakovic

Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario N1G 2W1

Corresponding Author: mbakovic{at}uoguelph.ca

CTP:phosphoethanolamine cytidylyltransferase (Pcyt2) catalyzes the rate-controlling reaction of the CDP-ethanolamine (Kennedy) pathway. We have previously established that Pcyt2 is encoded by a single gene that can be alternatively spliced from an internal exon into two transcripts, designated Pcyt2a and Pcyt2ß (Poloumienko et al, 2004, Gene, 325: 145-155). Little is currently known about the regulation of Pcyt2. Here we functionally express both murine Pcyt2 (mPcyt2) transcripts and investigate the roles of the two proteins in the regulation of mPcyt2 activity. We demonstrate that the tagged and purified a and ß proteins differ significantly in their kinetic properties. The Km of mPcyt2a for phosphoethanolamine was 318.4 mM, compared to 140.3 mM for mPcyt2ß. The maximal velocities of a and ß isoforms at saturating conditions for both substrates were 138.0 and 114.4 nmol/min/mmol of enzyme, respectively. When phosphoethanolamine was used at a fixed concentration of 1 mM, the Km of mPcyt2a for CTP was 102.0 mM and that of mPcyt2ß was 84.09 mM. Using a combination of non-denaturing PAGE, gel filtration chromatography, and immunoprecipitation, we provide evidence that mPcyt2a and -ß proteins can form both homo- and heterodimeric complexes. We show that alternative splicing of the mPcyt2 transcript is ubiquitous, but could also be regulated in a tissue-specific manner, producing a variable ratio of mPcyt2a:ß mRNAs. The expression of two distinct protein isoforms may be an important mechanism by which Pcyt2 activity is regulated.


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L. Zhu, C. Johnson, and M. Bakovic
Stimulation of the human CTP:phosphoethanolamine cytidylyltransferase gene by early growth response protein 1
J. Lipid Res., October 1, 2008; 49(10): 2197 - 2211.
[Abstract] [Full Text] [PDF]


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