title: Effect of buffer constituents on rat liver 3-hydroxy-3-methyl glutaryl coenzyme A reductase.
abstract: Rat liver microsomes prepared in Tris buffer exhibited 3 to 10 times higher 3-hydroxy-3-methyl glutaryl CoA reductase specific activity than microsomes prepared with potassium phosphate buffer. This higher activity was observed in rats killed during mid-light cycle, but microsomes from rats killed during mid-dark cycle showed no significant difference in enzyme activity between buffers. When microsomes prepared in the 2 different buffers were preincubated with ATP and MG++, enzyme activity was inhibited to the same extent. The cytosol fraction in each of the 2 different buffer preparations possessed similar phosphatase activity. The higher 3-hydroxy-3-methyl reductase activity in Tris buffer, therefore, does not appear to be due to differences in phosphorylation or dephosphorylation activity.
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D003600:Cytosol / Q000201:enzymology; D006903:Hydroxymethylglutaryl CoA Reductases / Q000378:metabolism*; D066298:In Vitro Techniques; D008027:Light; D008274:Magnesium / Q000494:pharmacology; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology*; D010710:Phosphates / Q000494:pharmacology*; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology*; D017680:Potassium Compounds; D051381:Rats; D014325:Tromethamine / Q000494:pharmacology*
chemical_list: D010710:Phosphates; D017680:Potassium Compounds; D014325:Tromethamine; D000255:Adenosine Triphosphate; C013216:potassium phosphate; D006903:Hydroxymethylglutaryl CoA Reductases; D010744:Phosphoric Monoester Hydrolases; D008274:Magnesium; D011188:Potassium