title: Influence of osmolytes, thin filaments, and solubility state on elasmobranch phosphofructokinase in vitro.
abstract: Skeletal muscle phosphofructokinase (PFK) purified from the thornback ray is rapidly inactivated by urea concentrations as low as 50 mM at pH values below 7.0. Urea-induced loss of PFK activity is not offset by trimethylamine-N-oxide. Protection against urea-inactivation in vivo, where urea concentration may approach 0.5 M, may be due to two effects. Filamentous (F) actin and muscle thin filaments moderately reduce the urea-induced loss of PFK activity. The binding of PFK to F-actin and to thin filaments is shown by ultracentrifugation experiments. PFK activity in vivo also may be stabilized in this species by the formation of a particulate enzyme form which is totally resistant to inactivation by physiological concentrations of urea.
mesh_terms: D000818:Animals; D003599:Cytoskeleton / Q000502:physiology*; D004355:Drug Stability; D005399:Fishes; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009132:Muscles / Q000201:enzymology*; D009994:Osmolar Concentration; D010732:Phosphofructokinase-1 / Q000302:isolation & purification / Q000378:metabolism*; D012995:Solubility; D014508:Urea / Q000494:pharmacology
chemical_list: D014508:Urea; D010732:Phosphofructokinase-1