Evidence for the presence of the reductive pentose phosphate cycle in a filamentous anoxygenic photosynthetic bacterium, Oscillochloris trichoides strain DG-6
Evidence for the presence of the reductive pentose phosphate cycle in a filamentous anoxygenic photosynthetic bacterium, Oscillochloris trichoides strain DG-6
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DOI：
10.1099/13500872-145-7-1743
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发表时间：
1999-07-01
期刊：
影响因子：
--
通讯作者：
Zyakun, AM
中科院分区：
文献类型：
--
作者：
Ivanovsky, RN;Fal, YI;Zyakun, AM
对丝状厌氧光合细菌DG-6的自养固定CO2的研究表明，与其他绿色细菌不同，该菌通过还原的戊糖磷酸循环来代谢CO2。在细胞提取液中检测到这一周期的两种关键酶--核酮糖1，5-二磷酸羧基酶/加氧酶和磷酸核酮酸激酶。核酮糖1，5-二磷酸依赖CO固定的主要产物是3-磷酸甘油酸。KCN是核酮糖-1，5-二磷酸羧化酶/加氧酶的竞争性抑制剂，它能完全抑制整个细胞和毛状藻细胞提取物对CO2的吸收。毛状藻光自养生长过程中碳-13/C-12碳同位素分馏为-19.7%，与以核酮糖-1，5-二磷酸羧化酶为主要羧化酶的自养生物的C-13/C-12碳同位素分馏相近。毛环菌细胞提取物中除I-氧代戊二酸脱氢酶外，其余均为三羧酸循环中的酶。在毛果野生稻DG-6细胞提取液中未发现乙醛分流的关键酶异柠檬酸裂解酶的活性。
Studies on autotrophic CO2 fixation by the filamentous anoxygenic photosynthetic bacterium Oscillochloris trichoides strain DG-6 demonstrated that, unlike other green bacteria, this organism metabolized CO2 via the reductive pentose phosphate cycle. Both key enzymes of this cycle - ribulose1,5-bisphosphate carboxylase/oxygenase and phosphoribulokinase - were detected in cell extracts. The main product of ribulose 1,5-bisphosphate-dependent CO, fixation was 3-phosphoglyceric acid. KCN, which is known to be a competitive inhibitor of ribulose-1,5-bisphosphate carboxylase/oxygenase, completely inhibited the CO2 assimilation by whole cells as well as by cell extracts of O. trichoides. The C-13/C-12 carbon isotope fractionation during photoautotrophic growth of O. trichoides was -19.7%, which is close to that obtained for autotrophic organisms that use ribulose-1,5-bisphosphate carboxylase as the primary carboxylation enzyme. Cell extracts of O. trichoides contained all the enzymes of the tricarboxylic acid cycle except I-oxoglutarate dehydrogenase. No activity of isocitrate lyase, a key enzyme of the glyoxylate shunt, was found in cell extracts of O. trichoides DG-6.