Del'vig A A, Tarasov A P, Debov S S
Vopr Med Khim. 1976 Sep-Oct;22(5):635-9.
Effect of cAMP on the activity of polynucleotide phosphorylase (PNPase) was studied in polyribosome fraction of rat liver tissue. Intraperitonel administration of cAMP or of theophilline into rats distinctly decreased the PNPase activity in the polyribosome fraction. The cAMP (1-10(-4) M) inhibited the enzymatic activity only by 8% in polyribosome fraction in vitro, as it was estimated by the reaction of phosphorolysis of endogenous RNA and polyA added. Any attempts were proved to be uncucessful to reveal cAMP, ATP-dependent proteinkinase in rat liver, responsible for the decrease in the PNPase activity in the polyribosome fraction. The cAMP inhibited the increase in the PNPase activity, coupled with protein biosynthesis in polyribosomes. Moreover, cAMP caused a decrease in the PNPase activity in reaction of polyA phosphorolysis and did not affect the rate of endogenous RNA phosphorolysis in polyribosome fraction, isolated from postmitochondrial fraction after incubation for 15 min at 30 degrees. The 3',5'-cyclo AMP (2-10(-6)-2-10(-4) M) stimulated incorporation of 14C-leucine into acid-insoluble material, when postmitochondrial fraction was incubated under the same conditions. The data obtained suggest that cAMP either inhibits specifically the PNPase synthesis or represses the coupled with protein biosynthesis formation of active "heavy" type of PNPase from less active "light" type.
在大鼠肝脏组织的多核糖体组分中研究了环磷酸腺苷（cAMP）对多核苷酸磷酸化酶（PNPase）活性的影响。给大鼠腹腔注射cAMP或茶碱可明显降低多核糖体组分中的PNPase活性。体外实验中，cAMP（1-10⁻⁴M）仅使多核糖体组分中的酶活性降低8%，这是通过内源性RNA和添加的多聚腺苷酸（polyA）的磷酸解反应估算得出的。所有试图在大鼠肝脏中揭示负责多核糖体组分中PNPase活性降低的cAMP、ATP依赖性蛋白激酶的尝试均未成功。cAMP抑制了与多核糖体中蛋白质生物合成相关的PNPase活性的增加。此外，cAMP导致多聚腺苷酸磷酸解反应中PNPase活性降低，并且不影响在30℃孵育15分钟后从线粒体后组分分离得到的多核糖体组分中内源性RNA的磷酸解速率。在相同条件下孵育线粒体后组分时，3',5'-环磷酸腺苷（2-10⁻⁶ - 2-10⁻⁴M）刺激了¹⁴C-亮氨酸掺入酸不溶性物质中。所获得的数据表明，cAMP要么特异性抑制PNPase的合成，要么抑制由活性较低的“轻”型向与蛋白质生物合成相关的活性“重”型PNPase的形成。
