Role of the regulatory subunit of bovine pyruvate dehydrogenase phosphatase.
Bovine pyruvate dehydrogenase phosphatase (PDP) is a Mg2+-dependent and Ca2+-stimulated heterodimer that is a member of the protein phosphatase 2C family and is localized to mitochondria. Insight into the function of the regulatory subunit of PDP (PDPr) has been gained. It decreases the sensitivity of the catalytic subunit of PDP (PDPc) to Mg2+. The apparent Km of PDPc for Mg2+ is increased about 5-fold, from about 0.35 mM to 1.6 mM. The polyamine spermine increases the sensitivity of PDP but not PDPc to Mg2+, apparently by interacting with PDPr. PDPc but not PDP can use the phosphopeptide RRAT(P)VA as a substrate. These observations are interpreted to indicate that PDPr blocks or distorts the active site of PDPc and that spermine produces a conformational change in PDPr that reverses its inhibitory effect. These findings suggest that PDPr may be involved in the insulin-induced activation of the mitochondrial PDP in adipose tissue, which is characterized by a decrease in its apparent Km for Mg2+.
Yan
J
J
Biochemical Institute, The University of Texas at Austin, 78712, USA.
Lawson
J E
JE
Reed
L J
LJ
D000273:Adipose Tissue / Q000187:drug effects / Q000201:enzymology; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002417:Cattle; D004789:Enzyme Activation / Q000187:drug effects; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology; D007668:Kidney / Q000187:drug effects / Q000201:enzymology; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism / Q000494:pharmacology; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology; D011487:Protein Conformation; D011769:Pyruvate Dehydrogenase (Lipoamide)-Phosphatase / Q000737:chemistry* / Q000378:metabolism*; D011768:Pyruvate Dehydrogenase Complex / Q000378:metabolism; D013096:Spermine / Q000494:pharmacology; D013379:Substrate Specificity
D007328:Insulin; D011768:Pyruvate Dehydrogenase Complex; D013096:Spermine; D011769:Pyruvate Dehydrogenase (Lipoamide)-Phosphatase; D008274:Magnesium; D002118:Calcium