title: Rat thyroid phosphofructokinase. Comparison of the regulatory and molecular properties with those of rat muscle enzyme.
abstract: The kinetic and molecular properties of rat thyroid phosphofructokinase (specific activity 134 units/mg) were compared with those of rat muscle phosphofructokinase (specific activity 135 units/mg). Thyroid and muscle phosphofructokinase showed similar sedimentation patterns in sucrose density gradients; their affinity for DEAE-cellulose was similar but not identical. A comparison of the kinetic properties revealed differences in the pH optima. Striking differences in the kinetic properties were shown below pH 7.4; the thyroid enzyme was less inhibited by ATP or citrate and more sensitive to activation by cyclic 3':5'-AMP than the muscle enzyme. A study of the effects of some cyclic as well as linear mononucleotides, such as cyclic AMP, cyclic IMP, cyclic GMP, cyclic CMP, cyclic UMP, 5'-AMP, and 3'-AMP on thyroid phosphofructokinase showed that at concentrations as low as 1 micrometer only cyclic AMP and cyclic IMP were able to activate thyroid enzyme in the presence of low fructose-6-P and high ATP concentrations.
mesh_terms: D000818:Animals; D002951:Citrates / Q000494:pharmacology; D004789:Enzyme Activation; D007700:Kinetics; D009132:Muscles / Q000201:enzymology*; D009928:Organ Specificity; D010732:Phosphofructokinase-1 / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats; D012265:Ribonucleotides / Q000494:pharmacology; D013961:Thyroid Gland / Q000201:enzymology*
chemical_list: D002951:Citrates; D012265:Ribonucleotides; D010732:Phosphofructokinase-1