Otani M, Fujita T, Umezawa C, Sano K
Biochim Biophys Acta. 1987 Jun 22;924(3):467-72. doi: 10.1016/0304-4165(87)90162-0.
The metabolic pathway of gluconate, a major product of glucose metabolism during spore germination, was investigated in Bacillus megaterium QM B1551. Compared to the parent, mutant spores lacking gluconokinase could not metabolize gluconate, whereas the revertant simultaneously restored the enzyme activity and the ability to metabolize it, indicating that gluconokinase was solely responsible for the onset of gluconate metabolism. To identify a further metabolic route for gluconate, we determined 14C yields in acetate and CO2 formed from [14C]gluconate, and found that experimental ratios of 14CO2/[14C]acetate obtained from [2-14C]gluconate and [3,4-14C]gluconate were not compatible with the ratios predicted from the Entner-Doudoroff pathway. In contrast, when CO2 release caused by recycling (approx. 30%) was corrected, the ratios almost agreed with those from the pentose cycle. Comparison of specific radioactivities in acetate also supported the conclusion that gluconate was metabolized via the pentose cycle, subsequently metabolized via the Embden-Meyerhof pathway, and finally degraded to acetate and CO2 without a contribution by the Krebs cycle.
在巨大芽孢杆菌QM B1551中研究了葡萄糖酸（孢子萌发期间葡萄糖代谢的主要产物）的代谢途径。与亲本相比，缺乏葡萄糖激酶的突变孢子无法代谢葡萄糖酸，而回复突变体同时恢复了酶活性和代谢葡萄糖酸的能力，这表明葡萄糖激酶是葡萄糖酸代谢起始的唯一原因。为了确定葡萄糖酸的另一条代谢途径，我们测定了由[14C]葡萄糖酸形成的乙酸盐和CO2中的14C产量，发现从[2-14C]葡萄糖酸和[3,4-14C]葡萄糖酸获得的14CO2/[14C]乙酸盐的实验比率与从恩特纳-杜德洛夫途径预测的比率不相符。相反，当校正由循环引起的CO2释放（约30%）时，这些比率几乎与戊糖循环的比率一致。乙酸盐中比放射性的比较也支持了以下结论：葡萄糖酸通过戊糖循环代谢，随后通过糖酵解途径代谢，最终降解为乙酸盐和CO2，而三羧酸循环没有参与。
