Role of sulfhydryl groups in phospholipid methylation reactions of cardiac sarcolemma |
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Authors: | Roland Vetter Jian Dai Nasrin Mesaeli Vincenzo Panagia Naranjan S Dhalla |
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Institution: | (1) Division of Cardiovascular Sciences St. Boniface General Hospital Research Centre, 351 Tache Avenue, R2H 2A6 Winnipeg, Manitoba, Canada;(2) Departments of Anatomy and Physiology, Faculty of Medicine, University of Manitoba Winnipeg, R2H 2A6, Canada |
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Abstract: | The effect of reagents that modify sulfur-containing amino acid residues in the phosphatidylethanolamine N-methyltransferase was studied in the isolated rat cardiac sarcolemma by employing S-adenosyl-L-methyl-3H]methionine as a methyl donor. Dithiothreitol protected the sulfhydryl groups in the membrane and caused a concentration- and time-dependent increase of phospholipid N-methylation at three different catalytic sites. This stimulation was highest (9-fold) in the presence of 1 MM MgCl2 and 0.1 µM S-adenosyl-L-methyl-3H]methionine at pH 8.0 (catalytic site 1), and was associated with an enhancement of Vmax without changes in Km for the methyl donor. Thiol glutathione was less stimulatory than dithiothreitol; glutathione disulfide inhibited the phosphatidylethanolamine N-methylation by 50%. The alkylating reagents, N-ethylmaleimide and methylmethanethiosulfonate, inhibited the N-methylation with IC5O of 6.9 and 14.1 µM, respectively; this inhibition was prevented by 1 mM dithiothreitol. These results indicate a critical role of sulfhydryl groups for the activity of the cardiac sarcolemmal phosphatidylethanolamine N-methyltransferase and suggest that this enzyme system in cardiac sarcolemma may be controlled by the glutathione/glutathione disulfide redox state in the cell.Abbreviations AdoMet
S-Adenosyl-L-methionine
- AdoHey
S-adenosyl-L-homocysteine
- DTNB
5,5dithiobis (2-nitrobenzoate)
- NEM
N-ethylmaleimide
- MMTS
methylmethanethiosulfonate
- DTT
dithiothreitol
- EDTA
Ethylenediaminetetraacetic acid
- GSH
glutathione
- GSSG
glutathione disulfide
- PE
phosphatidylethanolamine
- PMME
phosphatidyl-N-monomethylethamolamine
- PDME
phosphatidyl-N-dimethylethanolamine
- PC
phosphatidylcholine
- NPL
nonpolar lipids
- SL
sarcolemma |
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Keywords: | rat heart sarcolemma S-adenosyl-L-methionine phospholipid N-methylation neutral lipid methylation sulfhydryl groups |
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