Soluble and particulate forms of phosphoinositide phosphodiesterase in ox brain

摘要: Abstract 1. Phosphoinositide phosphodiesterase was recovered in both supernatant and well-washed particulate fractions of homogenates beef brain. 2. The membrane-bound enzyme solubilized with 2 M KC1 KCl-extracted enzymes were partially purified by ammonium sulphate fractionation adsorption to desorption from calcium phosphate gels. 3. Both could hydrolyse tri-, di- monophosphoinositides each case the products identified as diglycerides inositol phosphates. 4. optimum pH for monophosphoinositide hydrolysis 5.8, that diphosphoinositide 6.0, triphosphoinositide, 7.2–7.8, enzymes. Hydrolysis all three lipids stimulated cetyltrimethylammonium bromide, when added suitable molar proportions, characteristic substrate. Ca 2+ a better activator than cationic detergent. Calculation apparent K m values indicated that, enzymes, there no marked differences affinity any inositide substrates. Heat denaturation almost identical respect polyphosphoinositide but substrate appeared be slightly more labile enzyme.