title: Glycerolipid biosynthesis in rat adipose tissue. 11. Effects of polyamines on Mg2+-dependent phosphatidate phosphohydrolase.
abstract: The effect of polyamines (spermine, spermidine and putrescine) on the Mg2+-dependent phosphatidate phosphohydrolase was investigated. Phosphatidate phosphohydrolase activity was measured in the presence of aqueous dispersed phosphatidate as substrate, and the release of inorganic phosphate was taken as a measure of phosphatidate phosphohydrolase activity. In the presence of various polyamines there was activation of the Mg2+-dependent phosphatidate phosphohydrolase activity. Under this condition, the Km of enzyme towards phosphatidase decreased from 1.6 x 10(-4) to 9.8 x 10(-5) M and the Mg2+ requirement decreased from 5 to 0.5 mM. These polyvalent cations did not replace Mg2+, but potentiate the phosphohydrolase activity in the presence of Mg2+. The activation of Mg2+-dependent phosphatidate phosphohydrolase activity by polyamines was observed in the presence of 3-sn-phosphatidylcholine, suggesting that these modulators of phosphatidate phosphohydrolase activity may be acting through different mechanisms. These studies demonstrate that polyamines may be important regulators of Mg2+-dependent phosphatidate phosphohydrolase activity in adipose tissue.
mesh_terms: D000273:Adipose Tissue / Q000201:enzymology* / Q000378:metabolism; D000818:Animals; D003600:Cytosol / Q000201:enzymology; D005260:Female; D005989:Glycerides / Q000096:biosynthesis*; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology*; D008297:Male; D008861:Microsomes / Q000201:enzymology; D010711:Phosphatidate Phosphatase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D011073:Polyamines / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012995:Solubility; D013379:Substrate Specificity
chemical_list: D005989:Glycerides; D011073:Polyamines; D010744:Phosphoric Monoester Hydrolases; D010711:Phosphatidate Phosphatase; D008274:Magnesium