Paulus T J, Cramer C L, Davis R H
J Biol Chem. 1983 Jul 25;258(14):8608-12.
The polyamines putrescine, spermidine, and spermine are multivalent cations that bind to anionic cell constituents such as nucleic acids. Their distribution between free and bound states within the cell is not known. Such knowledge would be important in relation to the negative control of polyamine synthesis. We report a tracer experiment in which [14C]ornithine was added to logarithmically growing Neurospora crassa mycelia. The amount and the specific radioactivity of the three polyamines thereafter suggested that new molecules of spermidine were made preferentially from new molecules of putrescine, and that new molecules of spermine were made from new molecules of spermidine. The extent of mixing of new [14C]- and resident [12C]spermidine indicated that 70% or more of the resident spermidine was sequestered, and not immediately accessible to spermine synthase. Cell fractionation revealed that about 28% of the cellular spermidine was vacuolar, and nonexchangeable with [14C] spermidine added at the time of cell breakage. We suggest that the remainder of sequestered spermidine is bound strongly to anionic sites in the cell, and is relatively inactive in the control and synthesis of polyamines.
多胺腐胺、亚精胺和精胺是多价阳离子，可与阴离子细胞成分如核酸结合。它们在细胞内游离态和结合态之间的分布情况尚不清楚。此类知识对于多胺合成的负调控具有重要意义。我们报告了一项示踪实验，其中将[14C]鸟氨酸添加到对数生长期的粗糙脉孢菌菌丝体中。此后，三种多胺的量和比放射性表明，新的亚精胺分子优先由新的腐胺分子合成，而新的精胺分子由新的亚精胺分子合成。新的[14C] - 和留存的[12C]亚精胺的混合程度表明，70%或更多的留存亚精胺被隔离，精胺合酶无法立即接触到。细胞分级分离显示，约28%的细胞亚精胺存在于液泡中，在细胞破碎时不能与添加的[14C]亚精胺交换。我们认为，其余被隔离的亚精胺与细胞中的阴离子位点紧密结合，在多胺的调控和合成中相对不活跃。
