PHOSPHOPYRUVATE CARBOXYLASE ACTIVITY AND CARBON DIOXIDE FIXATION VIA C4 ACIDS OVER DIVISION CYCLE IN SYNCHRONIZED EUGLENA CULTURES
PHOSPHOPYRUVATE CARBOXYLASE ACTIVITY AND CARBON DIOXIDE FIXATION VIA C4 ACIDS OVER DIVISION CYCLE IN SYNCHRONIZED EUGLENA CULTURES
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DOI：
10.1007/bf00385213
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发表时间：
1971-01-01
期刊：
影响因子：
4.3
通讯作者：
MERRETT, MJ
中科院分区：
文献类型：
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作者：
CODD, GA;MERRETT, MJ
在分裂同步的纤细裸藻Z株培养物中测定了磷酸丙酮酸羧化酶的活性。酶活性的曲线基本上是“峰值酶”的曲线;在周期的光阶段活性增加，在早期暗阶段加倍，随后在接近暗阶段结束时活性大幅下降。暗二氧化碳固定没有平行的磷酸丙酮酸羧化酶活性的变化。二氧化碳固定速率在光照期增加了4倍，但在黑暗期下降，直到光照期开始时仅为2倍。虽然在整个分裂周期的所有阶段，磷酸丙酮酸羧化酶的比活性都大于核酮糖1-5二磷酸羧化酶的比活性，但C4酸不是光照下二氧化碳固定的早期产物，它们在细胞可溶性部分中所占的总14 C的比例也不超过一小部分。磷酸丙酮酸羧化酶（Phosphopyruvate carboxylase，PKC）在裸藻细胞质中的定位结果表明，该酶在藻细胞中的主要功能是为三羧酸循环提供回补序列。
Phosphoryruvate carboxylase activity was determined in division synchronizedEuglena gracilisstrain Z cultures. The profile of enzyme activity was essentially that of a “peak enzyme”; activity increased over the light phase of the cycle, doubling by early dark phase followed by a substantial decline in activity near the end of the dark phase. Dark carbon dioxide fixation did not parallel changes in phosphoryruvate carboxylase activity. The rate of carbon dioxide fixation increased fourfold over the light phase but decreased in the dark phase until it was only double the rate at the beginning of the light phase.Although the specific activity of phosphopyruvate carboxylase was greater than that of ribulose 1–5 diphosphate carboxylase inEuglenacell extracts at all stages over the division cycle C4acids were not an early product of carbon dioxide fixation in the light, neither did they ever account for more than a small proportion of the total14C present in the soluble fraction of the cells. Phosphopyruvate carboxylase was shown by the non-aqueous localization technique to be present in the cytoplasm inEuglena, and it is concluded that the main function of this enzyme in algal cells is to provide an anaplerotic sequence to the tricarboxylic acid cycle.