Paulus T J, Davis R H
J Bacteriol. 1981 Jan;145(1):14-20. doi: 10.1128/jb.145.1.14-20.1981.
Polyamine pools were measured under various conditions of high and low concentrations of cytosolic ornithine with the wild-type and mutant strains of Neurospora crassa. In minimal medium, the wild-type strain has 1 to 2 nmol of putrescine and approximately 14 nmol of spermidine per mg (dry weight); no spermine is found in N. crassa. Exogenous ornithine was found to cause a rapid, but quickly damped, increase in the rate of polyamine synthesis. This effect was greater in a mutant (ota) unable to catabolize ornithine. No turnover of polyamines was detected during exponential growth. Exogenous spermidine was not taken up efficiently by N. crassa; thus, the compound could not be used directly in studies of regulation. However, by nutritional manipulation of a mutant strain, aga, lacking arginase, cultures were starved for ornithine and thus ultimately for putrescine and spermidine. During ornithine starvation, the remaining putrescine pool was not converted to spermidine. The pattern of polyamine synthesis after restoration of ornithine to the polyamine-deprived aga strain indicated that, in vivo, spermidine regulates polyamine synthesis at the ornithine decarboxylase reaction. The results suggest that the regulatory process is a form of negative control which becomes highly effective when spermidine exceeds its normal level. The possible relationship between the regulation of polyamine synthesis and the ratio of free to bound spermidine is discussed.
在胞质鸟氨酸高低不同浓度的各种条件下，用粗糙脉孢菌的野生型和突变菌株测定了多胺池。在基本培养基中，野生型菌株每毫克（干重）含有1至2纳摩尔腐胺和约14纳摩尔亚精胺；在粗糙脉孢菌中未发现精胺。发现外源鸟氨酸会导致多胺合成速率迅速增加，但很快就会衰减。这种效应在无法分解代谢鸟氨酸的突变体（ota）中更为明显。在指数生长期间未检测到多胺的周转。粗糙脉孢菌对外源亚精胺的吸收效率不高；因此，该化合物不能直接用于调节研究。然而，通过对缺乏精氨酸酶的突变菌株aga进行营养操纵，培养物缺乏鸟氨酸，从而最终缺乏腐胺和亚精胺。在鸟氨酸饥饿期间，剩余的腐胺池没有转化为亚精胺。将鸟氨酸恢复到缺乏多胺的aga菌株后，多胺合成模式表明，在体内，亚精胺在鸟氨酸脱羧酶反应中调节多胺合成。结果表明，调节过程是一种负调控形式，当亚精胺超过其正常水平时，这种调控变得非常有效。文中还讨论了多胺合成调节与游离亚精胺与结合亚精胺比例之间的可能关系。
