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K Seyama

Publications and source records attributed to K Seyama.

49 records · Page 3Linked to original sources
PubMed1986

Phospholipid requirement of alkylglycerol monooxygenase from rat liver microsomes.

The alkylglycerol monooxygenase catalyzing the cleavage of the ether bond in alkylglycerol resides in rat liver microsomes. The enzyme preparation was freed of phospholipids by sodium deoxycholate treatment followed by gel filtration in the presence of deoxycholate. The removal of phospholipids markedly decreased the alkylglycerol monooxygenase activity. The activity of the delipidated enzyme, however, could be completely restored by the addition of phospholipid vesicles without detergent. When individual phospholipids were added, anionic phospholipids such as phosphatidylglycerol and diphosphatidylglycerol were the most effective. These findings, along with our previous observation of a similar effect of liposomes on the purified enzyme, indicate that the amphipathic nature of the protein is responsible for the lipid dependence of enzymatic activity.

Animals↗
PubMed1986

[Studies on acetyl-CoA:lyso platelet activating factor acetyltransferase of rat spleen microsomes--solubilization and substrate specificity].

Acetyl-CoA: lyso platelet activating factor (1-O-alkyl-2-lyso-sn-glycero-3-phosphorylcholine) acetyltransferase was solubilized from rat spleen microsomes with ultrasonic irradiation in the presence of 25% glycerol and partially purified by Sepharose 6B column chromatography. The overall yield of this procedures was approximately 26% and its specific activity was 1.7 times compared with that of original microsomes. The solubilized enzyme was extremely labile, but did not lose the activity for several weeks at -70 degrees C. The solubilized enzyme was remarkably susceptible to various kinds of metal ions. Furthermore, sulfhydryl reagents such as N-ethylmaleimide and p-chloromercuribenzoate profoundly inhibited the enzyme reaction, suggesting that the enzyme was -SH enzyme. The acetyltransferase activity was remarkably decreased by tryptic digestion of spleen microsomes, which indicated that the enzyme was located in the cytoplasmic surface of microsomal membranes. On the substrate specificity, the enzyme preferentially acetylated 1-O-hexadecyl-2-lyso-sn-glycero-3-phosphorylcholine and 1-O-octadecenyl-2-lyso-sn-glycero-3-phosphorylcholine as compared with other chain length at sn-1 position of lyso platelet activating factor, which may suggest that biologically potent molecular species of PAF are selectively synthesized. On the other hand, the enzyme also acetylated an acyl analog of lyso platelet activating factor. Some experimental results have shown that these two acetylation reaction presumably would be performed by the same enzyme.

Acetyl Coenzyme A↗