Springer Iranian Journal of Science and Technology (Sciences) 1028-6276 32 2 2008 06 01 ENZYMOLOGICAL CHARACTERISTICS OF PLASMA MEMBRANE PHOSPHATIDATE PHOSPHOHYDROLASE (PAP2) FROM RAT LIVER 117 127 2249 10.22099/ijsts.2008.2249 EN E. HEIDARIAN Department of Biochemistry, Ilam University of Medical Sciences, Ilam, I. R. of Iran B. HAGHIGHI Department of Biochemistry, Esfahan University of Medical Sciences, Esfahan, I. R. of Iran Journal Article 2005 04 17 Phosphatidate phosphohydrolase (PAP2b, fraction b) was purified from the plasma membrane of<br />rat liver cells. The Km for the surface concentration of phosphatidic acid was 0.43 mol%. The subunit of the<br />enzyme had an M.W. of 33.8 kDa using sodium dodecyl sulfate polyacrylamide gel electrophoresis. The<br />native enzyme shows a molecular weight of 182 kDa in a gel filtration column packed with Sephacryl S300 in<br />the presence of Triton X-100. The pH optima obtained for PAP2b were 5.5 and 7 in imidazole and Tris- HCl<br />buffers, respectively. The membrane homogenate enzyme (PAP2) consumed the lamellar (La) phase of<br />phosphatidate and was activated (approximately 3-fold) by Lubrol PX, CTAB and Tween 80 and inhibited by<br />Zn2+ and Mn2+. The inhibition was concentration dependent. These cations affected PAP2b activity through the phase transition of phosphatidate from lamellar (La) to inverted hexagonal (HII) form. Guanidine<br />hydrochloride and urea increased PAP2 activity (2-fold) up to 20mM concentrations by stabilizing the La<br />phase. Optimum activity of purified PAP2b was obtained at 3% trehalose and 7% sucrose. The data suggested that the stability of the La form of phosphatidate by detergent micelles may take place through surface dilution processes. https://ijsts.shirazu.ac.ir/article_2249_ac22fac795fce86a06d8b938d06bd63f.pdf