Prophospholipase A2 (ProPLA2)
|(Phosphatide 2-acyl hydrolase; EC 188.8.131.52)
Prophospholipase A2 (ProPLA2) catalyzes the hydrolysis of the fatty acid at the 2-position of phospholipids. The resulting product is called a lysophosphatide as described in the reaction below:
Phospholipid + H2O ------> Lysophosphatide + Fatty acid
Pancreatic PLA2 from ox and porcine have been purified and characterized. Liver lysosomes have been shown to contain several phospholipases A (Mellors, A. and A.L., Tappel, J. Lipid Res., 8, 479, 1967) and PLA2 from platelet membranes has also been studied and it could serve as a model system for the study of biological processes such as membrane transport and secretion (Billah, M.M., Lapetina, E.G. and P. Cuatrecasas, J. Biol. Chem., 255, No. 21, 10, 227, 1980). This enzyme could also be used for the determination of phopholipids.
Prophospholipase A2 (ProPLA2) is the inactive precursor of phopholipase A2 (PLA2) and full activity of the enzyme can be obtained by incubating ProPLA2 with trypsin at 1°C, pH 8.0 in the presence of 5 mM CaCl2. The ratio of trypsin to ProPLA2 should be about 1:2000 (w/w).
The proenzyme (ProPLA2) is prepared from porcine pancreas by a method involving chromatography. It could be used for studying the interesting phenomenon associated with the activation of the proenzyme where a heptapeptide is cleaved off by the action of trypsin (Pieterson, et al, Biochemistry, 13, 1455, 1974). The proenzyme could also be used as an accurate molecular weight marker (MW 14,100).
One unit of enzyme activity is defined as that amount of enzyme that will hydrolyze one micromole of L-a-phosphatidyl choline and fatty acid per minute at the appropriate pH and temperature.
The assay method is described by De Hass et al. (De Haas, H.; Postema, N.M.; Nieuwenhuizen, W. and L.L.M. VanDeenen, Biochim. Biophys. Acta, 159, 103, 1968) and by Desnuelle, et al (Desnuelle, P.; Constantin, M.J. and J. Baldy, Bull. Soc. Chim. Biol., 37, 285, 1955).