title: Factors effecting the solubilisation of stearoyl-coA desaturase of hen liver microsomes.
abstract: 1. The lipid requirement for maximum desaturase activity was investigated using acetone/water mixtures. It was shown that for maximum stearoyl-CoA desaturase activity of hen liver microsomes neither the total neutral lipid fraction nor 44% of the phospholipid fraction were required. 2. The effect of sodium deoxycholate, Triton X-100, Nonidet P-40 and Bio-solv on the enzyme activity indicated that the neutral detergents had a milder effect than the ionic detergent but both classes could cause considerable irreversible loss of activity. 3. The treatment of the microsomes with 2.5% (v/v) water in acetone greatly improved the effective solubilising power of Triton X-100. The yield of desaturase in the 100 000 X g supernatant obtained by treating the microsomal fraction in this way was strongly dependent upon protein concentration. Maximum solubilisation was achieved with25 mg protein per ml 1% (w/v) Triton X-100 in 0.1 M potassium phosphate buffer pH 7.4. 4. A comparison of the properties of the solubilised and membrane-bound enzyme was made by an investigation of: (i) the temperature and pH optimum, (ii) activation energy and (iii) the effect of inhibitors on the enzyme activity.
mesh_terms: D002731:4-Chloromercuribenzenesulfonate / Q000494:pharmacology; D000096:Acetone; D000818:Animals; D002645:Chickens; D003840:Deoxycholic Acid / Q000494:pharmacology; D044943:Fatty Acid Desaturases / Q000378:metabolism*; D005260:Female; D006863:Hydrogen-Ion Concentration; D008055:Lipids / Q000494:pharmacology; D008566:Membranes / Q000201:enzymology; D008862:Microsomes, Liver / Q000201:enzymology*; D011092:Polyethylene Glycols / Q000494:pharmacology; D011506:Proteins; D012995:Solubility; D013230:Stearoyl-CoA Desaturase / Q000378:metabolism*; D013501:Surface-Active Agents / Q000494:pharmacology; D013696:Temperature; D013816:Thermodynamics
chemical_list: D008055:Lipids; D011506:Proteins; D013501:Surface-Active Agents; D003840:Deoxycholic Acid; D000096:Acetone; D011092:Polyethylene Glycols; D002731:4-Chloromercuribenzenesulfonate; D044943:Fatty Acid Desaturases; D013230:Stearoyl-CoA Desaturase