title: Evidence for a role of sulfhydryl groups in catalytic activity and subunit interaction of the cyclic GMP-dependent protein kinase from silkworm.
abstract: Guanosine 3':5'-monophosphate-dependent protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) has been isolated from silkworm pupal fat body (Bombyx mori) which is devoid of any adenosine 3':5'-monophosphate-dependent protein kinase. The enzyme displayed catalytic properties which were roughly similar to those described for adenosine 3':5'-monophosphate-dependent protein kinase. This similarity has been found in substrate specificity, optimal Mg2+ dependency, polyamines effects and the lack of dependency upon sulfhydryl compound for activation by cyclic GMP. Treatment of the enzyme with sulfhydryl reagents, N-ethylmaleimide or p-chloromercuribenzoic acid, inhibited the catalytic activity as well as the dissociation of the binding and catalytic activities as shown by means of sucrose-density gradient ultracentrifugation. In the presence of cyclic GMP or histone, the disulfide-linked structure did not dissociate into separate subunits nor did it migrate as the holoenzyme but sedimented as an intermediate form carrying both binding and catalytic activities.
mesh_terms: D000818:Animals; D012831:Bombyx / Q000201:enzymology*; D002384:Catalysis; D006152:Cyclic GMP / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D046911:Macromolecular Substances; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism*; D011679:Pupa / Q000201:enzymology; D013438:Sulfhydryl Compounds / Q000378:metabolism*; D013439:Sulfhydryl Reagents / Q000494:pharmacology
chemical_list: D046911:Macromolecular Substances; D047428:Protein Kinase Inhibitors; D013438:Sulfhydryl Compounds; D013439:Sulfhydryl Reagents; D011494:Protein Kinases; D006152:Cyclic GMP