Abstract
The effect of polyamines (spermine, spermidine and putrescine) on the Mg 2+-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 Mg 2+-dependent phosphatidate phosphohydrolase activity. Under this condition, the K m of enzyme towards phosphatidate decreased from 1.6·10 −4 to 9.8·10 −5 M and the Mg 2+ requirement decreased from 5 to 0.5 mM. These polyvalent cations did not replace Mg 2+, but potentiate the phosphohydrolase activity in the presence of Mg 2+. The activation of Mg 2+-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 Mg 2+-dependent phosphatidate phosphohydrolase activity in adipose tissue.
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