Mullaney I, Clegg R A
Biochem J. 1984 May 1;219(3):801-9. doi: 10.1042/bj2190801.
Cyclic nucleotide phosphodiesterase activity in mammary tissue from rats in midlactation was resolved by DEAE-cellulose chromatography into three functionally distinct fractions: a Ca2+/calmodulin-stimulated cyclic GMP phosphodiesterase, a cyclic GMP-stimulated low-affinity cyclic nucleotide phosphodiesterase, and a high-affinity cyclic AMP-specific phosphodiesterase. The absolute activities and relative proportions of high- and low-affinity enzymes resemble those found, for example, in liver, as distinct from those in excitable tissues. Three functional characteristics are described which are peculiar to mammary-tissue phosphodiesterases. Firstly, the concentration of free Ca2+ required to achieve half-maximal activation of the Ca2+/calmodulin-stimulated phosphodiesterase is somewhat higher than for the analogous enzyme in other tissues; secondly, the activity of this enzyme towards cyclic AMP relative to that towards cyclic GMP is unusually low, and thirdly, the low-affinity cyclic nucleotide phosphodiesterase is inhibited by low concentrations of free Ca2+.
通过二乙氨基乙基纤维素色谱法,可将泌乳中期大鼠乳腺组织中的环核苷酸磷酸二酯酶活性解析为三个功能不同的组分:一种钙/钙调蛋白刺激的环鸟苷酸磷酸二酯酶、一种环鸟苷酸刺激的低亲和力环核苷酸磷酸二酯酶和一种高亲和力的环腺苷酸特异性磷酸二酯酶。高亲和力和低亲和力酶的绝对活性及相对比例类似于例如在肝脏中发现的情况,这与可兴奋组织中的情况不同。描述了乳腺组织磷酸二酯酶特有的三个功能特征。首先,使钙/钙调蛋白刺激的磷酸二酯酶达到最大激活一半所需的游离钙浓度略高于其他组织中的类似酶;其次,该酶对环腺苷酸的活性相对于对环鸟苷酸的活性异常低,第三,低亲和力环核苷酸磷酸二酯酶受到低浓度游离钙的抑制。