Reversible translocation of CTP:phosphocholine cytidylyltransferase from cytosol to membranes in the adult bovine liver around parturition.
The key regulatory enzyme of phosphatidylcholine (PC) synthesis, CTP:phosphocholine cytidylyltransferase (CT), is known to be activated in vitro by translocation from soluble to particulate fractions of the cell. In the present study the periparturient cow was chosen as a model to investigate whether translocation of CT can contribute to the regulation of PC synthesis in vivo. Between parturition and 1.5 weeks post-partum, the cytosolic CT activity in the liver of the adult animal decreased 1.9-fold, and this correlated with a 1.8-fold increase in microsomal CT activity. At that time, microsomal CT activity started to decline again whereas the cytosolic activity rose concomitantly until both activities reached their pre-partum values at 8 weeks post-partum. The activities of soluble and membrane-bound CTP:phosphoethanolamine cytidylyltransferase (ET), the analogous enzyme in the CDP-ethanolamine pathway, did not change significantly throughout this period. Whereas hepatic PC concentrations declined until about 2 weeks post-partum and thereafter gradually returned to pre-partum levels, the PC levels in very-low-density-lipoproteins, started to rise 2 weeks after the partus reaching a maximum of 219% of the original value at 8 weeks post-partum. These results strongly suggest that there is a reversible redistribution of CT between cytosol and membranes in a physiologically relevant animal model, supporting the concept that translocation of CT is occurring in vivo.
Bladergroen
B A
BA
Laboratory of Veterinary Biochemistry, Graduate School Animal Health, Utrecht University, P.O. Box 80.176, 3508 TD Utrecht, Netherlands.
Wensing
T
T
Van Golde
L M
LM
Geelen
M J
MJ
D000818:Animals; D001693:Biological Transport, Active; D002417:Cattle; D019916:Choline-Phosphate Cytidylyltransferase / Q000378:metabolism*; D003600:Cytosol / Q000201:enzymology; D005260:Female; D007743:Labor, Obstetric / Q000097:blood / Q000378:metabolism*; D008079:Lipoproteins, VLDL / Q000097:blood; D008099:Liver / Q000201:enzymology*; D008780:Methyltransferases / Q000378:metabolism; D008862:Microsomes, Liver / Q000201:enzymology; D008954:Models, Biological; D009713:Nucleotidyltransferases / Q000378:metabolism; D010713:Phosphatidylcholines / Q000096:biosynthesis; D050918:Phosphatidylethanolamine N-Methyltransferase; D010743:Phospholipids / Q000097:blood; D049590:Postpartum Period / Q000097:blood / Q000378:metabolism; D011247:Pregnancy; D012316:RNA Nucleotidyltransferases
D008079:Lipoproteins, VLDL; D010713:Phosphatidylcholines; D010743:Phospholipids; D008780:Methyltransferases; D050918:Phosphatidylethanolamine N-Methyltransferase; D009713:Nucleotidyltransferases; D012316:RNA Nucleotidyltransferases; C020126:Ethanolamine-phosphate cytidylyltransferase; D019916:Choline-Phosphate Cytidylyltransferase