Open AccessF-INDUCED CHANGES AND ITS REVERSAL BY ITP IN MEMBRANE TURBIDITY AND ADENYLATE CYCLASE ACTIVITY OF CHICK BRAIN MICROSOMES
Author(s) -
Takeo Asakawa,
Hiroshi Yoshida
Publication year - 1976
Publication title -
japanese journal of pharmacology/japanese journal of pharmacology
Language(s) - English
Resource type - Journals
eISSN - 1347-3506
pISSN - 0021-5198
DOI - 10.1254/jjp.26.233
Subject(s) - adenylate kinase , cyclase , gtp' , chemistry , incubation , membrane , turbidity , microsome , nucleotide , enzyme , medicine , endocrinology , biochemistry , biology , ecology , gene
The activation of adenylate cyclase by NaF was dependent on the previous incubation time and the concentration of F-. The activation by F- was irreversible and Mg2+ was required for the maximum effect. Turbidity of microsome suspension was also greatly increased by F- plus Mg2+. These effects on adenylate cyclase and membrane turbidity were specific for F- and F- saturation curves for both were similar, though Mg2+-saturation curves for both were dissimilar. The increase in turbidity induced by F- plus Mg2+ was rapidly reversed by ATP, GTP, ITP, UTP and CTP. However, ITP only, among all the triphospho-nucleotides tested, reversed the activity of adenylate cyclase previously activated by NaF plus MgC12. The activity of the enzyme reversed by ITP was not, however, re-enhanced by the presence of NaF in the assay medium. These results suggest the possiblity that F- induces a change in the membrane structure itself, and this change can be reversed by incubation with ITP. Consequently, adenylate cyclase may be conformed either to an activated or an unactivated state.