TY - JOUR ID - 31715 TI - MOLECULAR WEIGHT DETERMINATION AND METAL ION REQUIREMENT OF PHOSPHATIDATE PHOSPHOHYDROLASE PURIFIED FROM CYTOSOLIC FRACTION OF RAT LIVER JO - Journal of Sciences, Islamic Republic of Iran JA - JSCIENCES LA - en SN - 1016-1104 Y1 - 2002 PY - 2002 VL - 13 IS - 3 SP - EP - DO - N2 - Phosphatidate phosphohydrolase (PAP) from cytosolic fraction of rat liver was purified to homogeneity having specific activity of 5.14 U/mg protein. An activity staining procedure was developed to determine molecular weight of the enzyme on polyacrylamide gel electrophoresis using Ferguson plot. Molecular Weight (M.W.) of the active PAP was 298 KDa. SDS-PAGE analysis showed a M.W. of 47 KDa for PAP subunits. Active multimer of the enzyme, therefore, was calculated to be hexamer. Gel filtration on Sephadex G-100 column showed a M.W. of 850 KDa for PAP due to the protein aggregation on the matrix. The purified enzyme was inhibited by divalent cations such as Fe2+, Cu2+ and Ca2+ but requires Mg 2+ for its activity. The activity loss of PAP inhibited by cations was restored by Mg2+ on polyacrylamide gel. The data suggest that the active form of cytosolic PAP is a hexamer of identical subunits and that charge density plays an important role in enzyme-substrate interaction. Magnesium ion is probably the only divalent cation capable of generating proper enzyme-metal-substrate complex necessary for the catalytic activity. UR - https://jsciences.ut.ac.ir/article_31715.html L1 - https://jsciences.ut.ac.ir/article_31715_69d8f6af482a7baa2fe431e76fe4a0f3.pdf ER -