[Role of the sulfhydryl group in the thiamine pyrophosphokinase activity of the rat liver].
Amount and reactivity of SH-groups in thiamine pyrophosphokinase from rat liver tissue were studied using the mercaptide-forming reagents HgCl2 and p-chloromercury-benzoate (pCMB). Two types of SH-groups were found: the first--readily accessible and the second--partially concealed groups. Amount of these groups altered in presence of 8 M urea and 0.5% sodium dodecylsulfate. The enzymatic activity was inhibited by 30% after pCMB modification of the first type SH-groups and by 100% if second type SH-groups were blocked. All the substrates used, except of ATP, protected partially thiamine pyrophosphokinase against the inactivating effect of the reagent. The mercaptide-forming reagents exhibited dissimilar efficiency apparently due to different nature of the chemical bonds formed: pCMB developed the bond protein-S-HgR and HgCl2 formed--(protein-S)2Hg bond. The data obtained suggest that the SH-groups are localized close to the active site of thiamine pyrophosphokinase and that they participate in stabilization of the molecular structure of the enzyme.
D000494:Allosteric Regulation; D000818:Animals; D002729:Chloromercuribenzoates / Q000494:pharmacology; D003600:Cytosol / Q000201:enzymology; D004228:Dithionitrobenzoic Acid / Q000494:pharmacology; D008099:Liver / Q000201:enzymology*; D008627:Mercuric Chloride; D008628:Mercury / Q000494:pharmacology; D010770:Phosphotransferases / Q000378:metabolism*; D051381:Rats; D013438:Sulfhydryl Compounds / Q000378:metabolism*; D013439:Sulfhydryl Reagents / Q000494:pharmacology*; D013836:Thiamin Pyrophosphokinase / Q000037:antagonists & inhibitors / Q000378:metabolism*
D002729:Chloromercuribenzoates; D013438:Sulfhydryl Compounds; D013439:Sulfhydryl Reagents; D008627:Mercuric Chloride; D004228:Dithionitrobenzoic Acid; D010770:Phosphotransferases; D013836:Thiamin Pyrophosphokinase; D008628:Mercury
Rol' sul'fgidril'nykh grupp v fermentativnoĭ aktivnosti tiaminpirofosfokinazy pecheni krys.