title: pH-dependent amino acid induced conformational changes of rabbit muscle pyruvate kinase.
abstract: The interactions of L-Phe and L-Ala with rabbit muscle pyruvate kinase dependend upon the nature of divalent metal ions sutdied: Mg(II), Co(II), Mn(II), and Ni(II). L-phe inhibited all metal derivatives of the enzyme except Mn(II)--enzyme. L-Ala inhibited only Ni(II)--enzyme and had no effect on other metal derivatives. The inhibition by L-Phe could be partially or completely reversed by L-Ala for all metal derivatives. The mode of inhibition of pyruvate kinase by L-Phe depended upon pH as well as the nature of activating divalent metal ions. The sigmoidal response increased with increasing pH for all metal derivatives inhibited by L-Phe. L-Phe and L-Ala strongly perturbed the coordination sphere of enzyme bound Co(II), but not Ni(II). There were poor correlations between visible circular dichroic (cd) spectral changes and the corresponding kinetic changes. However, L-Phe and (or) L-Ala induced ultraviolet cd and difference absorption spectral changes, on the other hand, corresponded remarkably well with the kinetic observations.
mesh_terms: D000409:Alanine / Q000378:metabolism*; D000818:Animals; D002942:Circular Dichroism; D003035:Cobalt / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D009132:Muscles / Q000201:enzymology*; D009532:Nickel / Q000494:pharmacology; D010649:Phenylalanine / Q000378:metabolism*; D011487:Protein Conformation; D011770:Pyruvate Kinase / Q000378:metabolism*; D011817:Rabbits; D013056:Spectrophotometry, Ultraviolet
chemical_list: D003035:Cobalt; D008345:Manganese; D010649:Phenylalanine; D009532:Nickel; D011770:Pyruvate Kinase; D008274:Magnesium; D000409:Alanine