LIGAND-INDUCED CHANGES IN THE ACCESSIBILITY OF SULFHYDRYL-GROUPS OF NEUROSPORA-CRASSA PYRUVATE-KINASE

1. 1. The free sulphydryl groups of Neurospora pyruvate kinase were modified by reaction with a fluorogenic probe, 7-chloro-4-nitro-benzo-2-oxa-l,3-diazole (NBD-CT1). 2. 2. A maximum of four to five -SH groups/monomer was titrated in the presence of phosphate buffer. 3. 3. The extent of - SH reactivity was markedly influenced by the presence of substrates and allosteric modifiers, during the reaction with NBD-C1. 4. 4. The ligands and ligand combinations that shielded the - SHs of pyruvate kinase also protected its catalytic activity. © 1979.