THE PATHWAY OF ARGININE CATABOLISM IN GIARDIA-INTESTINALIS
THE PATHWAY OF ARGININE CATABOLISM IN GIARDIA-INTESTINALIS
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DOI：
10.1016/0166-6851(92)90197-r
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发表时间：
1992-03-01
影响因子：
1.5
通讯作者：
WILSON, JR
中科院分区：
文献类型：
--
作者：
SCHOFIELD, PJ;EDWARDS, MR;WILSON, JR
在贾第鞭毛虫中，精氨酸通过精氨酸二氢水解酶途径分解代谢。研究了该途径的酶（精氨酸脱亚氨酶、鸟胺酸转氨甲酰酶和氨基甲酸酯激酶）并确定了它们的基本动力学参数。精氨酸脱亚胺酶的比活力为270 ± 23 nmol min-1（mg蛋白质）-1;鸟氨酸氨甲酰转移酶，瓜氨酸利用方向170 +/- 22 nmol min-1（mg蛋白质）-1，并且在鸟氨酸利用方向上为2100 +/- 100 nmol min-1（mg蛋白）-1;和氨基甲酸酯激酶2100 +/-400 nmol min-1（mg蛋白）-1。这些酶的活性比报道的迷走毛滴虫中的酶的活性大10至250倍，迷走毛滴虫是报道精氨酸二氢水解酶途径的唯一其他寄生虫。G.通过从1 mM [C-14-胍基]精氨酸中释放（CO2）-C-14测定的肌酐为30 nmol min-1（mg蛋白）-1。该通量不受缬氨霉素（0.1 μ M）、尼日利亚菌素（3 μ M）、叠氮化物（5 mM）或氰化物（1 mM）的影响。通量仅轻微地受到高达10 mM浓度的葡萄糖的影响。相反，通过葡萄糖代谢的通量（由1 mM [1-C-14]葡萄糖释放的（CO2）-C-14测定）仅为2 nmol min-1（mg蛋白）-1，并且不受高达10 mM的精氨酸浓度的影响。这些观察结果表明，精氨酸和葡萄糖催化剂之间没有直接的代谢界面。从精氨酸流中获得的ATP势能是从葡萄糖流中获得的ATP势能的7-8倍，这为精氨酸在G.好吧有人建议，通过精氨酸水解酶途径的流量是能源生产的主要来源，特别是在厌氧条件下。
In Giardia intestinalis, arginine is catabolised by the arginine dihydrolase pathway. The enzymes of the pathway (arginine deiminase, ornithine transcarbamoylase and carbamate kinase) were investigated and their basic kinetic parameters determined. The specific activity of arginine deiminase was 270 +/- 23 nmol min-1 (mg protein)-1; ornithine transcarbamoylase, in the direction of citrulline utilisation 170 +/- 22 nmol min-1 (mg protein)-1, and in the direction of ornithine utilisation 2100 +/- 100 nmol min-1 (mg protein)-1; and carbamate kinase 2100 +/- 400 nmol min-1 (mg protein)-1. The activities of these enzymes are between 10 and 250 fold greater than those reported for the enzymes in Trichomonas vaginalis, the only other parasite in which the arginine dihydrolase pathway has been reported. The flux through the pathway in G. intestinalis, as determined by the liberation of (CO2)-C-14 from 1 mM [C-14-guanidino]arginine was 30 nmol min-1 (mg protein)-1. This flux was not affected by valinomycin (0.1-mu-M), nigericin (3-mu-M), azide (5 mM) or cyanide (1 mM). The flux was only marginally affected by glucose up to 10 mM concentration. Conversely, the flux through glucose metabolism, as determined by the release of (CO2)-C-14 from 1 mM [1-C-14]glucose was only 2 nmol min-1 (mg protein)-1, and was unaffected by arginine concentrations up to 10 mM. These observations suggest that there is no direct metabolic interface between arginine and glucose catabolism. The potential energy yield of ATP from the arginine flux is 7-8-fold greater than that from glucose, providing evidence for the prime importance of arginine in the energy economy of G. intestinalis. It is suggested that the flux through the arginine dihydrolase pathway is the major source of energy production, particularly in anaerobic conditions.