title: Effect of 22R-hydroxycholesterol on the action of sphingomyelinase from Bacillus cereus toward bovine erythrocytes.
abstract: The incorporation of 22R-hydroxycholesterol [(22R)-5-cholestene-3 beta,22-diol] into the bovine erythrocyte membranes remarkably enhanced the degradation of sphingomyelin in erythrocyte membranes by the action of sphingomyelinase from Bacillus cereus, causing much faster hemolysis of erythrocytes. The stimulative effect of 22R-hydroxycholesterol on the breakdown of sphingomyelin was maximal in the presence of Mg2+. On the other hand, in spite of the presence of 22R-hydroxycholesterol, the breakdown of sphingomyelin was inhibited by increasing concentrations of Ca2+. Also, the incorporation of 22R-hydroxycholesterol into the erythrocyte membranes facilitated the specific adsorption of the enzyme onto the surface of the erythrocyte membranes. The specific adsorption of sphingomyelinase amounted to 20-40% of the total activity in the presence of Mg2+ and the absence of divalent metal ions. In the presence of Ca2+, the incorporation of 22R-hydroxycholesterol enhanced the enzyme adsorption, exceeding more than 90% of the total activity. Therefore, the incorporation of 22R-hydroxycholesterol into bovine erythrocyte membranes remarkably accelerates the breakdown of sphingomyelin in the presence of Mg2+, and the specific adsorption of sphingomyelinase onto erythrocytes in the presence of Ca2+.
authors.affiliation: Faculty of Pharmaceutical Sciences, Nagoya City University, Aichi, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Tomita
authors.forename: J
authors.initials: J
authors.lastname: Togami
authors.forename: Y
authors.initials: Y
authors.lastname: Fujimoto
authors.forename: N
authors.initials: N
authors.lastname: Ikekawa
authors.forename: R
authors.initials: R
authors.lastname: Taguchi
authors.forename: H
authors.initials: H
authors.lastname: Ikezawa
mesh_terms: D000327:Adsorption; D000818:Animals; D001409:Bacillus cereus / Q000201:enzymology; D002417:Cattle; D004357:Drug Synergism; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000378:metabolism*; D006461:Hemolysis / Q000187:drug effects; D006888:Hydroxycholesterols / Q000494:pharmacology*; D008274:Magnesium; D013108:Sphingomyelin Phosphodiesterase / Q000493:pharmacokinetics*; D013109:Sphingomyelins / Q000378:metabolism*; D013696:Temperature
chemical_list: D006888:Hydroxycholesterols; D013109:Sphingomyelins; C003585:22-hydroxycholesterol; D013108:Sphingomyelin Phosphodiesterase; D008274:Magnesium