Phosphatidate Phosphohydrolase Catalyzes the Hydrolysis of Ceramide 1-Phosphate, Lysophosphatidate, and Sphingosine 1-Phosphate

A Mg2+-independent phosphatidate phosphohydrolase was purified from rat liver plasma membranes in two distinct forms, an anionic protein and a cationic protein. Both forms of the enzyme dephosphorylated phosphatidate, ceramide 1-phosphate, lysophosphatidate, and sphingosine 1-phosphate. When assayed...

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Bibliographic Details
Published in:The Journal of biological chemistry 1996-07, Vol.271 (28), p.16506-16509
Main Authors: Waggoner, David W., Gómez-Muñoz, Antonio, Dewald, Jay, Brindley, David N.
Format: Article
Language:English
Subjects:
Animals
Catalysis
Ceramides - metabolism
Ethylmaleimide - pharmacology
Hydrolysis
Kinetics
Liver - enzymology
Lysophospholipids - metabolism
Phosphatidate Phosphatase - drug effects
Phosphatidate Phosphatase - metabolism
Rats
Second Messenger Systems
Signal Transduction
Sphingosine - analogs & derivatives
Sphingosine - metabolism
Substrate Specificity
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Summary:A Mg2+-independent phosphatidate phosphohydrolase was purified from rat liver plasma membranes in two distinct forms, an anionic protein and a cationic protein. Both forms of the enzyme dephosphorylated phosphatidate, ceramide 1-phosphate, lysophosphatidate, and sphingosine 1-phosphate. When assayed at a constant molar ratio of lipid to Triton X-100 of 1:500, the apparent Km values of the anionic phosphohydrolase for the lipid substrates was 3.5, 1.9, 0.4, and 4.0 µM, respectively. The relative catalytic efficiency of the enzyme for phosphatidate, ceramide 1-phosphate, lysophosphatidate, and sphingosine 1-phosphate was 0.16, 0.14, 0.48, and 0.04 liter (min·mg)−1, respectively. The hydrolysis of phosphatidate was inhibited competitively by ceramide 1-phosphate, lysophosphatidate, and sphingosine 1-phosphate. The Ki(app) values were 5.5, 5.9, and 4.0 µM, respectively. The hydrolysis of phosphatidate by the phosphohydrolase conformed to a surface dilution kinetic model. It is concluded that the enzyme is a lipid phosphomonoesterase that could modify the balance of phosphatidate, ceramide 1-phosphate, lysophosphatidate, and sphingosine 1-phosphate relative to diacylglycerol, ceramide, monoacylglycerol, and sphingosine, respectively. The enzyme could thus play an important role in regulating cell activation and signal transduction.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.271.28.16506