Epstein P M, Silverman P M
J Bacteriol. 1978 Sep;135(3):968-75. doi: 10.1128/jb.135.3.968-975.1978.
Extracts of vegetative cells of Blastocladiella emersonii contain 5% or less of the cyclic AMP phosphodiesterase activity in zoospore extracts. This difference in activity could be accounted for entirely by an increase in the differential rate of phosphodiesterase synthesis during sporulation, beginning after a lag period of about 60 min and extending for at least an additional 90 min into the 4-h sporulation process. To examine the relation between enzyme synthesis and cyclic nucleotide metabolicm, we determined the substrate specificity of phosphodiesterase synthesized during sporulation and partially purified from zoospores. Zoospore extracts contain two components, separable by gel filtration chromatography, with cyclic AMP phosphodiesterase activity. The larger component accounts for 20% of the total activity and the smaller component for 80%. Both components show essentially an absolute substrate specificity for cyclic AMP among several cyclic purine and cyclic pyrimidine nucleotides tested. Nevertheless, we found no change in the total cyclic AMP content of sporulating cells before, during, or after enzyme activity increased. We speculate that some other component of cyclic AMP metabolism or function limits the rate of cyclic AMP hydrolysis in sporulating cells.
艾美球囊霉营养细胞提取物中的环磷酸腺苷磷酸二酯酶活性在游动孢子提取物中占5%或更低。这种活性差异完全可以由孢子形成过程中磷酸二酯酶合成差异速率的增加来解释，这一过程在约60分钟的延迟期后开始，并在4小时的孢子形成过程中至少再持续90分钟。为了研究酶合成与环核苷酸代谢之间的关系，我们测定了孢子形成过程中合成并从游动孢子中部分纯化的磷酸二酯酶的底物特异性。游动孢子提取物含有两种通过凝胶过滤色谱可分离的成分，具有环磷酸腺苷磷酸二酯酶活性。较大的成分占总活性的20%，较小的成分占80%。在测试的几种环嘌呤和环嘧啶核苷酸中，这两种成分对环磷酸腺苷都表现出基本上绝对的底物特异性。然而，我们发现在酶活性增加之前、期间或之后，正在形成孢子的细胞的总环磷酸腺苷含量没有变化。我们推测环磷酸腺苷代谢或功能的其他一些成分限制了正在形成孢子的细胞中环磷酸腺苷的水解速率。
