Benninghoff B, Lehmann V, Eck H P, Dröge W
Institute of Immunology and Genetics, German Cancer Research Center, Heidelberg.
Int Immunol. 1991 May;3(5):413-7. doi: 10.1093/intimm/3.5.413.
Activated macrophages exert strong arginase (ASE) activity that converts L-arginine into ornithine, the key precursor for putrescine and polyamine biosynthesis. Macrophages were previously also shown to generate nitric oxide that is derived from the guanido group of arginine by the oxidative deiminase (OAD) reaction. In view of the physiological importance of ornithine and putrescine, we now investigated whether interferon-gamma (IFN-gamma), a principal stimulator of the OAD activity, may lead to the accumulation of the deiminated derivative citrulline at the expense of ornithine production, or whether the carbon backbone could be reutilized for the production of arginine and ornithine. Our experiments show that murine peritoneal macrophages treated with IFN-gamma in combination with tumor necrosis factor (TNF) or bacterial lipopolysaccharide (LPS) generate substantial amounts of citrulline as identified by amino acid analyzer and by thin-layer chromatography. Also, labeled citrulline is generated from [14C]L-arginine but not from [14C]L-ornithine. This suggests that macrophages have little or no capacity to convert ornithine into arginine. In the absence of IFN-gamma, TNF and LPS stimulate the conversion of arginine into ornithine but not citrulline. However, when TNF or LPS stimulated macrophages are simultaneously treated with IFN-gamma, ornithine production is relatively inhibited by the strong OAD reaction that competes with the ASE reaction for its substrate L-arginine. IFN-gamma thus down-regulates the availability of ornithine and putrescine. The lipid A precursor IA also induces, in conjunction with IFN-gamma, the production of citrulline but fails to stimulate the generation of ornithine.
活化的巨噬细胞具有很强的精氨酸酶（ASE）活性，该酶可将L-精氨酸转化为鸟氨酸，而鸟氨酸是腐胺和多胺生物合成的关键前体。此前还发现巨噬细胞可通过氧化脱亚氨酶（OAD）反应从精氨酸的胍基生成一氧化氮。鉴于鸟氨酸和腐胺的生理重要性，我们现在研究了OAD活性的主要刺激因子γ干扰素（IFN-γ）是否会导致以鸟氨酸生成减少为代价的瓜氨酸脱亚胺衍生物的积累，或者碳骨架是否可被重新利用来生成精氨酸和鸟氨酸。我们的实验表明，用IFN-γ联合肿瘤坏死因子（TNF）或细菌脂多糖（LPS）处理的小鼠腹腔巨噬细胞，通过氨基酸分析仪和薄层色谱法鉴定出会产生大量瓜氨酸。此外，标记的瓜氨酸是由[14C]L-精氨酸生成的，而不是由[14C]L-鸟氨酸生成的。这表明巨噬细胞几乎没有或没有将鸟氨酸转化为精氨酸的能力。在没有IFN-γ的情况下，TNF和LPS刺激精氨酸转化为鸟氨酸，但不刺激生成瓜氨酸。然而，当TNF或LPS刺激的巨噬细胞同时用IFN-γ处理时，鸟氨酸的生成会因强烈的OAD反应而相对受到抑制，该反应与ASE反应竞争其底物L-精氨酸。因此，IFN-γ下调了鸟氨酸和腐胺的可用性。脂质A前体IA与IFN-γ一起也诱导瓜氨酸的产生，但不能刺激鸟氨酸的生成。
