title: Regulation of pyruvate dehydrogenase kinase activity from pig kidney cortex.
abstract: The activity of pyruvate dehydrogenase (PDH) kinase in the purified PDH complex from pig kidney is sensitive to changes in ionic strength. The enzyme has optimum activity within a small range of ionic strength (0.03-0.05 M). An increase in ionic strength from 0.04 M to 0.2 M lowers the activity of PDH kinase by 32% and decreases the Km for ATP from 25 microM to 10 microM. At constant ionic strength (0.15 M) the enzyme has optimum activity over a broad pH range (7.2-8.0). The PDH kinase is stimulated 2.2-fold by 20 mM-K+, whereas Na+ even at high concentration (80 mM) has no effect on the enzyme activity. The stimulation of PDH kinase by K+ is not dependent on pH and ionic strength. PDH kinase is inhibited by HPO4(2-) in the presence of K+, whereas HPO4(2-) has no effect on the activity of this enzyme in the absence of K+. HPO4(2-) at concentrations of 2 and 10 mM inhibits PDH kinase by 28% and 55% respectively. The magnitude of this inhibition is not dependent on the ATP/ADP ratio. Inhibition by HPO4(2-) in the concentration range 0-10 mM is non-competitive with respect to ATP, and becomes mixed-type at concentrations over 10 mM. The Ki for HPO4(2-) is 10 mM. When HPO4(2-) is replaced by SO4(2-), the same effects on the activity of PDH kinase are observed. PDH kinase is also inhibited by Cl-. In the presence of 80 mM-Cl- the PDH kinase is inhibited by 40%. The inhibition by Cl- is not dependent on K+. In conclusion, we postulate that changes in phosphate concentrations may play a significant role in the regulation of PDH kinase activity in vivo.
authors.affiliation: Department of Biochemistry, University of Texas Health Science Center, San Antonio 78284-7760.
authors.forename: T
authors.initials: T
authors.lastname: Pawelczyk
authors.forename: M S
authors.initials: MS
authors.lastname: Olson
mesh_terms: D000818:Animals; D002712:Chlorides / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007672:Kidney Cortex / Q000201:enzymology*; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism; D009994:Osmolar Concentration; D010710:Phosphates / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D011768:Pyruvate Dehydrogenase Complex / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism; D013431:Sulfates / Q000378:metabolism; D013552:Swine
chemical_list: D002712:Chlorides; D010710:Phosphates; D047428:Protein Kinase Inhibitors; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D011768:Pyruvate Dehydrogenase Complex; D013431:Sulfates; D012964:Sodium; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D008274:Magnesium; D011188:Potassium