The 45- and 104-kDa forms of phosphatidate phosphatase from Saccharomyces cerevisiae are regulated differentially by phosphorylation via cAMP-dependent protein kinase.
Evidence is presented that demonstrated that the 45- and 104-kDa forms of phosphatidate phosphatase from Saccharomyces cerevisiae (Morlock, K. R., McLaughlin, J. J., Lin, Y.-P., and Carman, G. M. (1991) J. Biol. Chem. 266, 3586-3593) were regulated differentially by phosphorylation. Purified 45-kDa phosphatidate phosphatase was phosphorylated by cAMP-dependent protein kinase whereas purified 104-kDa phosphatidate phosphatase was not phosphorylated. cAMP-dependent protein kinase catalyzed the phosphorylation of pure 45-kDa phosphatidate phosphatase at a serine residue which resulted in a stimulation (2.4-fold) of phosphatidate phosphatase activity. Alkaline phosphatase catalyzed the dephosphorylation of pure 45-kDa phosphatidate phosphatase which resulted in an inhibition (1.3-fold) of phosphatidate phosphatase activity. Results of studies using mutants (bcy1 and cyr1) defective in cAMP-dependent protein kinase activity corroborated the results of the phosphorylation studies using pure preparations of phosphatidate phosphatase. The 45-kDa phosphatidate phosphatase phosphorylated in vitro and in vivo had phosphopeptides in common. The activation of the GAL10-RAS2val19 allele in mutant cells resulted in an increase in the synthesis of diacylglycerols and triacylglycerols. These results were consistent with the phosphorylation and activation of 45-kDa phosphatidate phosphatase by cAMP-dependent protein kinase in vivo.
Quinlan
J J
JJ
Department of Food Science, Cook College, New Jersey Agricultural Experiment Station, Rutgers University, New Brunswick 08903.
Nickels
J T
JT
Wu
W I
WI
Lin
Y P
YP
Broach
J R
JR
Carman
G M
GM
D000483:Alleles; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D005838:Genotype; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008954:Models, Biological; D008970:Molecular Weight; D010449:Peptide Mapping; D010711:Phosphatidate Phosphatase / Q000302:isolation & purification / Q000378:metabolism*; D010750:Phosphoproteins / Q000302:isolation & purification; D010766:Phosphorylation; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D018631:ras Proteins
D005656:Fungal Proteins; D007527:Isoenzymes; D010750:Phosphoproteins; D011494:Protein Kinases; D010711:Phosphatidate Phosphatase; D018631:ras Proteins