KINETIC-PROPERTIES OF LIVER AND MUSCLE PYRUVATE-KINASE OF A MARINE TELEOST, SEA BASS (DICENTRARCHUS-LABRAX L)

Liver PK had hyperbolic saturation curves with both substrates and was not sensitive to alanine, but was inhibited by ATP (I-50 = 6 mM). Bot h white and red muscle PK showed hyperbolic saturation curves with PEP and ADP, and were not activated by FDP but were inhibited by ATP (I-5 0 values were 2.3 and 5.6 mM, respectively). Varying Mg2+ concentratio ns in muscle and liver PK always showed sigmoidal kinetics, whereas wi th Mn2+ only the liver PK saturation curve was sigmoidal. Ca2+ was an inhibitor of both liver and muscle PK. CU2+ and Zn2+ had an inhibitory effect on liver and muscle PK. The I-50 values were of the same order but slightly lower for liver.