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Selective labelling of phosphorylase kinase with fluorescein isothiocyanate
Author(s) -
Sotiroudis Theodore G.,
Nikolaropoulos Stathis
Publication year - 1984
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(84)81210-7
Subject(s) - fluorescein isothiocyanate , fluorescein , chemistry , trypsin , phosphorylase kinase , enzyme , biochemistry , isothiocyanate , microbiology and biotechnology , protein subunit , kinase , glycogen phosphorylase , biology , fluorescence , physics , quantum mechanics , gene
Fluorescein isothiocyanate (FITC) is a highly specific inhibitor of rabbit muscle phosphorylase kinase. The rapid inhibition process is accompanied by an almost exclusive incorporation of fluorescein into the α sub‐unit. A molar ratio of 0.8 mol FITC per mol α subunit for a 60% inhibited kinase was calculated. Mg 2+ and Mg 2+ ‐ATP completely block the inhibitory effect of FITC, but ATP, ADP and Ca 2+ have no significant effect on FITC inhibition. Trypsin‐activated phosphorylase kinase is not inactivated by FITC, while the fluorescein‐modified enzyme can be activated by digestion with trypsin to the same level of activity of trypsin‐activated unmodified enzyme.