Two diverse effects of poly(L‐lysine) on rabbit skeletal muscle phosphorylase kinase: stimulation of autophosphorylation and inhibition of its activity

Abstract

Polylysine greatly stimulated the autophosphorylation of phosphorylase kinase from rabbit skeletal muscle. When fully autophosphorylated, about 14 mol of phosphate per tetramer (alpha beta gamma delta) were incorporated in the presence of polylysine, which was twice as much as those observed without polylysine. In contrast to this stimulatory effect of polylysine on the autophosphorylation, polylysine strongly inhibited the conversion reaction of phosphorylase b to a. The inhibition is competitive with a Ki of 2.3 micrograms/ml. No effects of polylysine were observed on the activities of phosphorylase and cAMP-dependent protein kinase.