title: Regulation of enzyme activity in the hibernator. A kinetic and spectroscopic study of muscle pyruvate kinase from the Arctic ground squirrel.
abstract: Pyruvate kinase skeletal muscle of the Arctic ground squirrel was purified to homogeneity. The purified enzyme variants from the summer-active and winter hibernating squirrel appear to be identical with a near-neutral pI of 6.9 and a molecular weight of 234,000 as determined by gel filtration chromatography on Bio-Gel A-0.5m. Evidence for subunit interaction during inhibition by L-phenylalanine is demonstrated with ultraviolet derivative spectroscopy. A model for this interaction and its importance for a regulatory role are discussed. The absence of a temperature break in the Arrhenius plot for the pyruvate kinase reaction, the kinetic and physical data, and the near-neutral pI, suggest an amino acid composition that conserves the overall geometry and resultant kinetic behavior which render regulation of the enzyme insensitive to temperature.
mesh_terms: D000818:Animals; D002980:Climate; D006605:Hibernation; D007700:Kinetics; D009124:Muscle Proteins / Q000302:isolation & purification; D009132:Muscles / Q000201:enzymology*; D011770:Pyruvate Kinase / Q000302:isolation & purification / Q000378:metabolism*; D012589:Sciuridae / Q000378:metabolism*; D013057:Spectrum Analysis; D013696:Temperature
chemical_list: D009124:Muscle Proteins; D011770:Pyruvate Kinase