END PRODUCTS AND ENZYME LEVELS OF AEROBIC GLUCOSE FERMENTATION IN TRYPANOSOMATIDS
END PRODUCTS AND ENZYME LEVELS OF AEROBIC GLUCOSE FERMENTATION IN TRYPANOSOMATIDS
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DOI：
10.1016/0166-6851(85)90074-x
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发表时间：
1985-01-01
影响因子：
1.5
通讯作者：
CANNATA, JJB
中科院分区：
文献类型：
--
作者：
CAZZULO, JJ;DECAZZULO, BMF;CANNATA, JJB
克氏锥虫（外鞭毛体），Crithidia fasciculata和墨西哥利什曼原虫（前鞭毛体）生长在脑-心-胰蛋白酶培养基补充热灭活胎牛血清。T. cruzi和C. fasciculata在对数生长期完全利用葡萄糖，而L. Mexicana仅在对数期结束时和稳定期开始时使用大量的碳水化合物。在所有情况下，葡萄糖消耗导致琥珀酸和更少量的乙酸的排泄。C. fasciculata和L. mexicana产生的丙酮酸含量很低，C. fasciculata产生乙醇，乙醇在葡萄糖耗尽后再次被吸收并代谢。乳酸和苹果酸没有产生。采用超声破碎法破碎细胞，测定了全匀浆中碳水化合物和氨基酸催化剂的关键酶活性。磷酸烯醇式丙酮酸羧激酶存在于三种生物中;墨西哥的比活度最高。该酶的活性在葡萄糖消耗过程中达到最大，葡萄糖耗尽后略有下降。这表明该酶所起的作用是糖酵解，而不是产酶;后者是大多数高等生物的情况。己糖激酶和丙酮酸激酶在C. fasciculata和T. cruzi在葡萄糖消耗。L.在整个实验期间处于活跃糖酵解的墨西哥，呈现出两种酶的最高比活性。另一方面，柠檬酸合成酶在C. fasciculata，T. cruzi，而L.墨西哥人。NAD连接的谷氨酸脱氢酶在C. fasciculata和T. cruzi后，葡萄糖耗尽，这表明分解代谢的作用的酶。这种增加与葡萄糖消耗后两种生物体的NH3产量增加相吻合。另一方面，NADP连接的谷氨酸脱氢酶在葡萄糖耗尽时出现最大值，然后再次下降，这表明该酶具有分解代谢作用。两种谷氨酸脱氢酶在L. mexicana;这与该生物体的整个培养过程中的低NH3产量很好地吻合。这一结果与目前关于锥虫好氧葡萄糖发酵机理的观点一致，表明在所用的实验条件下，T。cruzi和C. fasciculata使用葡萄糖优先于氨基酸的增长。
Trypanosoma cruzi (epimastigotes), Crithidia fasciculata and Leishmania mexicana (promastigotes) were grown in a brain-heart-tryptose medium supplemented with heat-inactivated fetal calf serum. T. cruzi and C. fasciculata utilized glucose completely during the log phase of growth, whereas L. mexicana used significant amounts of the carbohydrate only at the end of the log phase and at the beginning of the stationary phase. In all cases glucose consumption resulted in excretion of succinate, and much smaller amounts of acetate. C. fasciculata and L. mexicana produced very small amounts of pyruvate, C. fasciculata produced ethanol, which was taken up again and metabolysed after glucose was exhausted. Lactate and malate were not produced. The cells were disrupted by sonic disintegration, and the activities of some key enzymes of carbohydrate and amino acid catabolism were assayed in the whole homogenates. Phosphoenolpyruvate carboxykinase was present in the three organisms; L. mexicana presented the highest specific activity. The activity of this enzyme was maximal during glucose consumption, and slightly decreased after glucose was exhausted. This suggests that the role played by the enzyme is glycolytic and not gluconeogenic; the latter is the case in most higher organisms. Hexokinase and pyruvate kinase presented their highest levels in C. fasciculata and T. cruzi during glucose consumption. L. mexicana, which was in active glycolysis during the whole experimental period, presented the highest specific activities of both enzymes. Citrate synthase, on the other hand, increased in C. fasciculata and, to a lesser extent, in T. cruzi, after glucose was exhausted; the enzyme could not be detected in L. mexicana. The NAD-linked glutamate dehydrogenase increased considerably in C. fasciculata and T. cruzi after glucose was exhausted, suggesting a catabolic role for the enzyme. This increase coincided with an increase in NH3 production by both organisms after glucose consumption. The NADP-linked glutamate dehydrogenase, on the other hand, presented a maximum about the time when glucose was exhausted, and then decreased again, which suggests a catabolic role for the enzyme. Both glutamate dehydrogenases had low activities in L. mexicana; this fits in well with the low NH3 production throughout the culture of this organism. The results are in good agreement with current ideas on the mechanism of aerobic glucose fermentation by trypanosomatids and suggest that, under the experimental conditions used, both T. cruzi and C. fasciculata used glucose preferentially over amino acids for growth.