XXXX -activated, calmodulin-dependent protein kinase activity in @entity291 thyroid cytosol.

@entity6105 @entity2644 @entity460 @entity141 @entity291 @entity214
@entity291 thyroid 100,000 X g supernatant contained @entity460 -activated, calmodulin-dependent protein kinase (PK-CaM) activity. The PK-CaM was partially purified using ion-exchange chromatography and characterized. PK-CaM, using casein as exogenous substrate, was not stimulated by @entity141 (0-500 microM) or calmodulin (1-10 micrograms) by themselves, but was stimulated by the combination of the two by 100%. The activation of the enzyme by @entity141 and calmodulin was dose-dependent with maximal stimulation evident at 1 microM free- @entity141 and 3 micrograms calmodulin. Both @entity2644 and @entity6105 inhibited the thyroid enzyme in a dose-related manner. The molecular weight (MW) of the PK-CaM, based on gel filtration, was approximately 500,000. PK-CaM could also be demonstrated using endogenous thyroid cytosol proteins as substrate. Separation of these 32P-labelled proteins by @entity214 -PAGE and subsequent autoradiography revealed that one major protein of approximately 56,000 MW was phosphorylated by PK-CaM. In some experiments, a second, less-intense protein band of approximately 64,000 MW was also phosphorylated. Evidence is presented, suggesting that these two protein bands may result from the autophosphorylation of the PK-CaM holoenzyme. These results offer a molecular mechanism, in addition to protein kinase C, by which @entity141 effects may be mediated in thyroid.
