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S-adenosyl-L-methionine-mediated enzymatic methylations in the rat retinal membranes. 1994

B V Sastry, and P S Vidaver, and V E Janson, and J J Franks
Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, Tennessee.

Enzymatic step-wise methylation of membrane phosphatidylethanolamine (PE) to phosphatidyl-N-methylethanolamine (PME) and then phosphatidyl-choline (PC) has been known to alter membrane properties and responsiveness of cells for activation of receptors by chemical transmitters. Conversion of PE to PME and PME to PC in the presence of S-adenosyl-L-methionine (SAM) are catalyzed by two phospholipid N-methyltransferases, PMT I and PMT II, of which PMT I is the rate limiting enzyme. Retina is a good neuronal model for chemical transmission. However, retina was not studied for PMT activity. Therefore, we studied the rat retina for PMT I activity. Methylation of PE in the rat retinal sonicates was assayed using 3H-SAM (2 microM) at 37 degrees C in Tris-glycylglycine buffer (50 mM, pH 8.0) and methylated phospholipids were extracted with chloroform/methanol/HCl (2/1/0.02, v/v) and separated by thin layer chromatography on Silica Gel G plates. Chromatograms were developed in a solvent system of propionic acid/n-propyl alcohol/chloroform/water (2/2/1/1, v/v). This study gave the following results: (a) the total methylated phospholipids were (M +/- SE, N = 5) 19.90 +/- 4.03 fmol/mg protein/min; (b) the major methylated phospholipid was PME (4.21 +/- 0.68 fmol/mg protein/min; (c) the fatty acid methylesters formed by fatty acid carboxymethylase (FACM) which accumulated in the solvent front amounted to 18.82 +/- 2.84 fmol/mg protein/min. Both PMT I and FACM were inhibited by S-adenosyl-L-homocysteine (I50, 1.2-5 microM). These observations indicate that rat retina contains both PMTs and FACM.

UI MeSH Term Description Entries
D008745 Methylation Addition of methyl groups. In histo-chemistry methylation is used to esterify carboxyl groups and remove sulfate groups by treating tissue sections with hot methanol in the presence of hydrochloric acid. (From Stedman, 25th ed) Methylations
D008780 Methyltransferases A subclass of enzymes of the transferase class that catalyze the transfer of a methyl group from one compound to another. (Dorland, 28th ed) EC 2.1.1. Methyltransferase
D010714 Phosphatidylethanolamines Derivatives of phosphatidic acids in which the phosphoric acid is bound in ester linkage to an ethanolamine moiety. Complete hydrolysis yields 1 mole of glycerol, phosphoric acid and ethanolamine and 2 moles of fatty acids. Cephalin,Cephalins,Ethanolamine Phosphoglyceride,Ethanolamine Phosphoglycerides,Ethanolamineglycerophospholipids,Phosphoglyceride, Ethanolamine,Phosphoglycerides, Ethanolamine
D012160 Retina The ten-layered nervous tissue membrane of the eye. It is continuous with the OPTIC NERVE and receives images of external objects and transmits visual impulses to the brain. Its outer surface is in contact with the CHOROID and the inner surface with the VITREOUS BODY. The outer-most layer is pigmented, whereas the inner nine layers are transparent. Ora Serrata
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D012435 S-Adenosylhomocysteine 5'-S-(3-Amino-3-carboxypropyl)-5'-thioadenosine. Formed from S-adenosylmethionine after transmethylation reactions. S Adenosylhomocysteine,Adenosylhomocysteine, S
D012436 S-Adenosylmethionine Physiologic methyl radical donor involved in enzymatic transmethylation reactions and present in all living organisms. It possesses anti-inflammatory activity and has been used in treatment of chronic liver disease. (From Merck, 11th ed) AdoMet,Ademetionine,FO-1561,Gumbaral,S Amet,S-Adenosyl-L-Methionine,S-Adenosylmethionine Sulfate Tosylate,SAM-e,Samyr,FO 1561,FO1561,S Adenosyl L Methionine,S Adenosylmethionine,S Adenosylmethionine Sulfate Tosylate
D017207 Rats, Sprague-Dawley A strain of albino rat used widely for experimental purposes because of its calmness and ease of handling. It was developed by the Sprague-Dawley Animal Company. Holtzman Rat,Rats, Holtzman,Sprague-Dawley Rat,Rats, Sprague Dawley,Holtzman Rats,Rat, Holtzman,Rat, Sprague-Dawley,Sprague Dawley Rat,Sprague Dawley Rats,Sprague-Dawley Rats
D050918 Phosphatidylethanolamine N-Methyltransferase An enzyme that catalyses three sequential METHYLATION reactions for conversion of phosphatidylethanolamine to PHOSPHATIDYLCHOLINE. Cephalin N-Methyltransferase,PHET Methyltransferase II,Phosphatidylethanolamine Methyltransferase,Phosphatidylethanolamine N-Methyltransferase-2,Phosphatidylethanolamine-Methyltransferase II,Phosphatidylethanolamine-Phosphatidylcholine N-Methyltransferase,Phospholipid Methyltransferase II,S-Adenosylmethionine Phosphatidylethanolamine N-Methyltransferase,Cephalin N Methyltransferase,Methyltransferase II, PHET,Methyltransferase II, Phospholipid,Methyltransferase, Phosphatidylethanolamine,N-Methyltransferase, Cephalin,N-Methyltransferase, Phosphatidylethanolamine,N-Methyltransferase, Phosphatidylethanolamine-Phosphatidylcholine,N-Methyltransferase, S-Adenosylmethionine Phosphatidylethanolamine,N-Methyltransferase-2, Phosphatidylethanolamine,Phosphatidylethanolamine Methyltransferase II,Phosphatidylethanolamine N Methyltransferase,Phosphatidylethanolamine N Methyltransferase 2,Phosphatidylethanolamine N-Methyltransferase, S-Adenosylmethionine,Phosphatidylethanolamine Phosphatidylcholine N Methyltransferase,S Adenosylmethionine Phosphatidylethanolamine N Methyltransferase
D051381 Rats The common name for the genus Rattus. Rattus,Rats, Laboratory,Rats, Norway,Rattus norvegicus,Laboratory Rat,Laboratory Rats,Norway Rat,Norway Rats,Rat,Rat, Laboratory,Rat, Norway,norvegicus, Rattus

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