Abstract
Phosphorylase kinase from human polymorphonuclear leukocytes was investigated in a gel filtered crude preparation ( 17 000 × g supernatant ). It was found to exist in two forms, one (the phosphorylated form) more active than the other (the dephosphorylated form). Interconversion between the two forms was carried out by a cyclic AMP dependent proten kinase and phosphoprotein phosphatase, respectively. The ratio of activity measured at pH 8.0 and 6.0 was 0.36 the non-activated and 0.83 for the activated form, which is in contrast to the behaviour of phosphorylase kinase from muscle. K m app for the substrate phosphorylase b was 650 U/ml and 85 U/ml for the non-activated and activated form, respectively, whereas K m app for ATP was 0.03 mM and identical for the two forms. The non-activated form of phosphorylase kinase was activated by Ca 2+ in the range 10 −7–5 · 10 −6 M, which may have physiological importance, whereas the activated form was insensitive to variations in Ca 2+ concentration between 10 −9 and 10 −3 M.
Published Version
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