Hand SC, Somero GN. Influence of osmolytes, thin filaments, and solubility state on elasmobranch phosphofructokinase in vitro.
THE JOURNAL OF EXPERIMENTAL ZOOLOGY 1984;
231:297-302. [PMID:
6237173 DOI:
10.1002/jez.1402310216]
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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.
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