title: Concerning the coidentity of phosphatidic acid phosphohydrolase and phosphatidylglycerophosphate phosphohydrolase in rat lung lamellar bodies.
abstract: The properties of the phosphatidylglycerophosphate phosphohydrolase activity in lamellar bodies from rat lung have been compared with the properties of the activities responsible for the degradation of aqueously-dispersed phosphatidic acid (PAaq) and membrane-bound phosphatidic acid (PAmb). Subcellular fractionation studies revealed that the phosphatidylglycerophosphate phosphohydrolase activity and the PAaq-dependent phosphatidic acid phosphohydrolase activity were predominantly associated with the mitochondrial and microsomal fractions, while the PAmb-dependent phosphohydrolase activity was associated with the cytosol. Although the lamellar body fraction contained less than 1% of the total activity, the phosphatidic acid phosphohydrolase activities associated with this fraction could not be explained by contamination with microsomes or cytosol. The three activities exhibited similar heat inactivation profiles at 55 degree C. However, differences in the responses of these activities to the presence of iodoacetate, p-chloromercuriphenyl sulphonate, mercaptoethanol, mercaptoethanol plus MgCl2, and Triton X-100 indicated that the enzymes responsible for these activities may be distinct. Furthermore, addition of up to a ten-fold greater amount of PAaq did not seriously affect the hydrolysis of phosphatidylglycerophosphate. These results indicate that the phosphatidic acid phosphohydrolase and phosphatidylglycerophosphate phosphohydrolase activities in rat lung lamellar bodies are not necessarily catalyzed by the same protein.
mesh_terms: D000818:Animals; D006358:Hot Temperature; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D010711:Phosphatidate Phosphatase / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D011650:Pulmonary Alveoli / Q000201:enzymology* / Q000648:ultrastructure; D011663:Pulmonary Surfactants / Q000096:biosynthesis; D051381:Rats; D011919:Rats, Inbred Strains; D013347:Subcellular Fractions / Q000201:enzymology
chemical_list: D011663:Pulmonary Surfactants; D010744:Phosphoric Monoester Hydrolases; C026991:phosphatidylglycerophosphatase; D010711:Phosphatidate Phosphatase; D008274:Magnesium