Phosphorylase kinase from human polymorphonuclear leukocytes.
Phosphorylase kinase from human polymorphonuclear leukocytes was investigated in a gel filtered crude preparation (17,000 x 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 protein kinase and phosphoprotein phosphatase, respectively. The ratio of activity measured at pH 8.0 and 6.0 was 0.36 for the non-activated and 0.83 for the activated form, which is in contrast to the behaviour of phosphorylase kinase from muscle. Km app for the substrate phosphorylase b was 650 U/ml and 85 U/ml for the non-activated and activated form, respectively, whereas Km app for ATP was 0.03 mM and identical for the two forms. The non-activated form of phosphorylase kinase was activated by Ca2+ in the range 10(-7)--5 . 10(-6) M, which may have physiological importance, whereas the activated form was insensitive to variations in Ca2+ concentration between 10(-9) and 10(-3) M.
D002118:Calcium / Q000494:pharmacology; D004789:Enzyme Activation; D006801:Humans; D007527:Isoenzymes / Q000097:blood; D007700:Kinetics; D009504:Neutrophils / Q000201:enzymology*; D010764:Phosphorylase Kinase / Q000097:blood*; D010763:Phosphorylase b; D014357:Trypsin
D007527:Isoenzymes; D010763:Phosphorylase b; D010764:Phosphorylase Kinase; D014357:Trypsin; D002118:Calcium