Department of Biochemistry and Biotechnology, Royal Institute of Technology, S-100 44, Stockholm, Sweden.
Cytotechnology. 1998 Mar;26(2):91-102. doi: 10.1023/A:1007963003607.
Spodoptera frugiperda (Sf9) insect cells proliferate in a cystine-free medium, with the same growth rate, reaching the same final cell density, as in a cystine-containing medium, provided that the inoculum is taken from a pre-culture sufficiently early, at 47-53 h. With an inoculum from a 103 h culture an extended lag phase accompanied by cell death was observed during the first 50 h of cystine-free culture, even though the culture had been adapted to cystine-free conditions for 10 passages. Cystine-free cultures seeded with a 103 h inoculum had lower growth rates and reached lower final cell densities than corresponding cystine-supplied cultures. Cysteine biosynthesis occurs from methionine via the β-cystathionine pathway. More methionine was consumed by the cells in cystine-free media, and cystathionine was secreted when methionine and cystine were supplied in excess. The data suggest that cysteine biosynthesis is up-regulated in proliferating cells but down-regulated when the cells enter the stationary phase.In cultures supplied with cystine (10-100 mg 1(-1)), the specific uptake rate and total consumption of cystine, as well as the uptake of glutamate, glutamine and glucose increased with increasing cystine concentrations. These results are interpreted in view of system x (c) (-) , a concentration dependent amino acid transporter. Similarly, the consumption of amino acids transported by system L (ile, leu, val, tyr) was enhanced in cystine-containing cultures, as compared to cystine-free cultures. Uptake of cystine, methionine and system L amino acids ceases abruptly in all cultures, even before growth ceased. The specific growth rate starts to decline early during the growth phase, but this growth behaviour could not be correlated to the depletion of nutrients. We therefore propose that the observed growth pattern is a result of (auto)regulatory events that control both proliferation and metabolism.
草地贪夜蛾（Sf9）昆虫细胞在不含半胱氨酸的培养基中增殖，其生长速度与含半胱氨酸的培养基相同，最终细胞密度也相同，只要接种物是在 47-53 小时的预培养中尽早取出的。然而，当接种物来自于 103 小时的培养物时，在不含半胱氨酸的培养物中，即使已经适应了 10 次无半胱氨酸的条件，在最初的 50 小时也会观察到一个延长的迟滞期和细胞死亡。无半胱氨酸培养物的接种物来自于 103 小时的培养物，其生长速度较慢，最终细胞密度也低于相应的含半胱氨酸的培养物。半胱氨酸生物合成是从蛋氨酸通过β-胱硫醚途径发生的。无半胱氨酸的培养基中细胞消耗了更多的蛋氨酸，当蛋氨酸和半胱氨酸供应过剩时，细胞会分泌胱硫醚。数据表明，半胱氨酸生物合成在增殖细胞中上调，但当细胞进入静止期时下调。在供应半胱氨酸（10-100mg1（-1））的培养物中，特定的半胱氨酸摄取率和总消耗量，以及谷氨酸、谷氨酰胺和葡萄糖的摄取率都随着半胱氨酸浓度的增加而增加。这些结果与系统 x（c）（-）有关，这是一种依赖浓度的氨基酸转运体。同样，在含有半胱氨酸的培养物中，与无半胱氨酸的培养物相比，系统 L（异亮氨酸、亮氨酸、缬氨酸、酪氨酸）所运输的氨基酸的消耗也得到了增强。所有培养物中的半胱氨酸、蛋氨酸和系统 L 氨基酸的摄取都会突然停止，甚至在生长停止之前。比生长率在生长阶段早期就开始下降，但这种生长行为不能与营养物质的消耗相关联。因此，我们提出观察到的生长模式是控制增殖和代谢的（自动）调节事件的结果。
