Calmodulin and Ca2+‐ and calmodulin‐dependent protein kinase were identified in the rat anterior pituitary gland. The concentration of calmodulin was 1.18 ± 0.11 μg/mg protein (n = 7) in the cytosol fraction. The calmodulin of the anterior pituitary gland co‐migrated with brain calmodulin on sodium dodecyl sulfate polyacrylamide gel electrophoresis. The Ka value of the partially purified enzyme for Ca2+ was 3.3 μ.M in the presence of 0.30μ.M calmodulin. Trifluoperazine and chlorpromazine, calmodulin‐interacting agents, inhibited enzyme activity, with Ki values of 1.3 and 2.6 x 10‐5M, respectively. The enzyme was resolved into two peaks of activity, with sedimentation coefficients of 5.5 S and 16.5 S, by sucrose density gradient centrifugation. At least nine proteins were phosphorylated by the enzyme in a Ca2+‐ and calmodulin‐dependent manner. In light of these results, the possibility that calmodulin and the calmodulin‐activatable protein kinase system are involved in the mediation of the Ca2+ effect on hormone release from the anterior pituitary gland must be given consideration.
|Number of pages||8|
|Journal||Journal of Neurochemistry|
|Publication status||Published - 1983 Apr|
- Anterior pituitary gland
- Ca‐ and calmodulin‐dependent protein kinase
- Stimulus‐secretion coupling.
ASJC Scopus subject areas
- Cellular and Molecular Neuroscience