Goldberg B, Rattendi D, Yarlett N, Lloyd D, Bacchi C J
Department of Chemistry and Physical Sciences, Pace University, New York, New York 10038, USA.
J Eukaryot Microbiol. 1997 Jul-Aug;44(4):352-8. doi: 10.1111/j.1550-7408.1997.tb05677.x.
The fate of methionine in eukaryotic cells is divided between protein synthesis and the branched pathway encompassing polyamine synthesis, methylation of proteins and lipids, and transsulphuration reactions. Aside from protein synthesis, the first step to all other uses of methionine is conversion to S-adenosylmethionine. Blockade of polyamine synthesis in African trypanosomes by the ornithine decarboxylase inhibitor DL-alpha-difluoromethylornithine (Ornidyl, DFMO) the AdoMet decarboxylase inhibitor 5'-[[(Z)-4-amino-2-butenyl]-methylamino]-5'-deoxyadenosine or the protein methylase inhibitor sinefungin induces dramatic increases in intracellular AdoMet. In a previous study, distribution and pool sizes of [35S] or [U-14C]methionine were followed in bloodform trypanosomes as incorporation into the total TCA precipitable fractions. In the present study, the effects of pretreatment with DFMO (1 mM), MDL 73811 (1 microM) and sinefugin (2 nM) on [35S] and [U-14C]methionine incorporation were studied in blood forms. DFMO or MDL 73811 pretreatment increased protein methylation 1.5-fold through incorporation of [U14C]methionine, while sinefungin caused a 40% reduction of incorporation. The increases in incorporation of [U-14C]methionine due to DFMO and MDL 73811 were reduced 40% to 70% by including cold AdoMet (1 mM) in the incubation medium, an indication of AdoMet transport by bloodform trypanosomes and the utilization of [U-14C]methionine as AdoMet. Exogenous AdoMet had no effect on [35S]methionine incorporation. The agents studied are curative for African trypanosomiasis infections, either clinically (DFMO) or in model infections (MDL 73811, sinefungin) and thus highlight interference with AdoMet metabolism and methylation reactions as biochemical consequences of these agents.
在真核细胞中，甲硫氨酸的去向分为用于蛋白质合成以及参与包括多胺合成、蛋白质和脂质甲基化以及转硫反应在内的分支途径。除蛋白质合成外，甲硫氨酸用于所有其他用途的第一步是转化为S-腺苷甲硫氨酸。鸟氨酸脱羧酶抑制剂DL-α-二氟甲基鸟氨酸（Ornidyl，DFMO）、腺苷甲硫氨酸脱羧酶抑制剂5'-[[(Z)-4-氨基-2-丁烯基]-甲基氨基]-5'-脱氧腺苷或蛋白质甲基化酶抑制剂杀稻瘟菌素对非洲锥虫多胺合成的阻断会导致细胞内腺苷甲硫氨酸显著增加。在先前的一项研究中，追踪了血形式锥虫中[35S]或[U-14C]甲硫氨酸的分布和库大小，作为其掺入总三氯乙酸可沉淀部分的情况。在本研究中，研究了用DFMO（1 mM）、MDL 73811（1 microM）和杀稻瘟菌素（2 nM）预处理对血形式锥虫中[35S]和[U-14C]甲硫氨酸掺入的影响。DFMO或MDL 73811预处理通过掺入[U14C]甲硫氨酸使蛋白质甲基化增加了1.5倍，而杀稻瘟菌素导致掺入减少了40%。通过在孵育培养基中加入冷腺苷甲硫氨酸（1 mM），由于DFMO和MDL 73811导致的[U-14C]甲硫氨酸掺入增加减少了40%至70%，这表明血形式锥虫对腺苷甲硫氨酸的转运以及将[U-14C]甲硫氨酸用作腺苷甲硫氨酸。外源性腺苷甲硫氨酸对[35S]甲硫氨酸掺入没有影响。所研究的这些药物对非洲锥虫病感染具有治疗作用，无论是在临床方面（DFMO）还是在模型感染中（MDL 73811、杀稻瘟菌素），因此突出了干扰腺苷甲硫氨酸代谢和甲基化反应是这些药物的生化后果。
