title: Insulin stimulates the dephosphorylation of phosphothreonine from fat-pad ATP-citrate lyase.
abstract: ATP-citrate lyase is phosphorylated in vivo at three amino acid residues on two peptide sequences (peptides a and b). Insulin action is known to increase the phosphorylation of peptide a. To study the effect of insulin on peptide b phosphorylation ATP-citrate lyase was radiolabeled in vivo by incubating fat pads with 32Pi. Following "cold chase", insulin action decreased the calculated specific radioactivity of peptide b to less than 30% of control whereas the specific radioactivity of peptide a increased 5-6 fold. The insulin induced decrease in peptide b phosphorylation was mainly due to a decrease in phosphothreonine phosphorylation. Isoproterenol treatment increased peptide a phosphorylation 4-6 fold but did not decrease peptide b phosphorylation. Specific radioactivity of ATP did not change significantly with hormone treatment. These results suggest that insulin action increases the dephosphorylation of peptide b by increasing the activity of a putative phosphothreonine phosphatase.
mesh_terms: D001275:ATP Citrate (pro-S)-Lyase / Q000378:metabolism*; D000273:Adipose Tissue / Q000187:drug effects / Q000201:enzymology*; D000595:Amino Acid Sequence; D000818:Animals; D007328:Insulin / Q000494:pharmacology*; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D010446:Peptide Fragments / Q000032:analysis; D010766:Phosphorylation; D010769:Phosphothreonine / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013912:Threonine / Q000031:analogs & derivatives*; D014357:Trypsin
chemical_list: D007328:Insulin; D010446:Peptide Fragments; D010769:Phosphothreonine; D013912:Threonine; D001275:ATP Citrate (pro-S)-Lyase; D014357:Trypsin; D007545:Isoproterenol