Daniel Steven L, Pilsl Christine, Drake Harold L
Department of Biological Sciences, Eastern Illinois University, Charleston, IL 61920, USA.
FEMS Microbiol Lett. 2004 Feb 9;231(1):39-43. doi: 10.1016/S0378-1097(03)00924-8.
Whole-cell and cell-extract experiments were performed to study the mechanism of oxalate metabolism in the acetogenic bacterium Moorella thermoacetica. In short-term, whole-cell assays, oxalate consumption was low unless cell suspensions were supplemented with CO(2), KNO(3), or Na(2)S(2)O(3). Cell extracts catalyzed the oxalate-dependent reduction of benzyl viologen. Oxalate consumption occurred concomitant to benzyl viologen reduction; when benzyl viologen was omitted, oxalate was not appreciably consumed. Based on benzyl viologen reduction, specific activities of extracts averaged 0.6 micromol oxalate oxidized min(-1) mg protein(-1). Extracts also catalyzed the formate-dependent reduction of NADP(+); however, oxalate-dependent reduction of NADP(+) was negligible. Oxalate- or formate-dependent reduction of NAD(+) was not observed. Addition of coenzyme A (CoA), acetyl-CoA, or succinyl-CoA to the assay had a minimal effect on the oxalate-dependent reduction of benzyl viologen. These results suggest that oxalate metabolism by M. thermoacetica requires a utilizable electron acceptor and that CoA-level intermediates are not involved.
进行了全细胞和细胞提取物实验，以研究产乙酸细菌嗜热栖热菌中草酸盐代谢的机制。在短期全细胞测定中，除非细胞悬液补充有CO₂、KNO₃或Na₂S₂O₃，否则草酸盐消耗较低。细胞提取物催化了草酸盐依赖的苄基紫精还原。草酸盐消耗与苄基紫精还原同时发生；当省略苄基紫精时，草酸盐没有明显消耗。基于苄基紫精还原，提取物的比活性平均为0.6微摩尔草酸盐氧化分钟⁻¹毫克蛋白质⁻¹。提取物还催化了甲酸盐依赖的NADP⁺还原；然而，草酸盐依赖的NADP⁺还原可以忽略不计。未观察到草酸盐或甲酸盐依赖的NAD⁺还原。向测定中添加辅酶A（CoA）、乙酰辅酶A或琥珀酰辅酶A对草酸盐依赖的苄基紫精还原影响最小。这些结果表明，嗜热栖热菌的草酸盐代谢需要一种可利用的电子受体，并且CoA水平的中间产物不参与其中。
