RESUMEN
Actin has been shown to be a potent activator of the enzymatic hydrolysis of cellulose, its addition to the reaction mixture leading to an increase in the hydrolysis rate of up to 6-7 fold. The action of actin is directed primarily towards endoglucanases of cellulase complexes. The degree of activation varies in relation to the cellulases from different microbial sources. The activation of the enzymatic hydrolysis of an insoluble cellulose by actin does not affect the Michaelis constant but increases the maximum velocity of the reaction. Increasing the actin concentration leads to a linear increase in the activation effect which indicates a rather poor binding of actin with the cellulases under study.
Asunto(s)
Actinas/farmacología , Celulasa/metabolismo , Animales , Celulosa/metabolismo , Cromatografía por Intercambio Iónico , Activación Enzimática , Hidrólisis , Cinética , Músculos/análisis , Conejos , Trichoderma/enzimologíaRESUMEN
The activation of muscle phosphorylase kinase b by actin has been studied. F-actin which is polymerized by 2 mM MgCl2 is a more effective activator of phosphorylase kinase than F-actin polymerized by 50 mM KCl. There is evidence suggesting that the activation of phosphorylase kinase by actin is not due to trace contamination of actin preparations with calmodulin: (1) Troponin I and trifluoperazine inhibit the activation of phosphorylase kinase by calmodulin but do not inhibit the activation of phosphorylase kinase by F-actin. (2) The activation induced by saturating concentrations of calmodulin and actin is additive both at pH 8.2 and at pH 6.8. (3) The activation of phosphorylase kinase by calmodulin and actin has different pH profiles. An addition of F-actin does not affect the apparent Km value for ATP but increases the sensitivity to phosphorylase b and the value of Vmax.