Adachi Osao, Hours Roque A, Shinagawa Emiko, Akakabe Yoshihiko, Yakushi Toshiharu, Matsushita Kazunobu
Department of Biological Chemistry, Faculty of Agriculture, Yamaguchi University.
Biosci Biotechnol Biochem. 2011;75(9):1801-6. doi: 10.1271/bbb.110339. Epub 2011 Sep 7.
In our previous study, a new microbial reaction yielding 4-keto-D-arabonate from 2,5-diketo-D-gluconate was identified with Gluconacetobacter liquefaciens RCTMR 10. It appeared that decarboxylation and dehydrogenation took place together in the reaction. To analyze the nature of the reaction, investigations were done with the membrane fraction of the organism, and 4-keto-D-arabinose was confirmed as the direct precursor of 4-keto-D-arabonate. Two novel membrane-bound enzymes, 2,5-diketo-D-gluconate decarboxylase and 4-keto-D-aldopentose 1-dehydrogenase, were involved in the reaction. Alternatively, D-arabonate was oxidized to 4-keto-D-arabonate by another membrane-bound enzyme, D-arabonate 4-dehydrogenase. More directly, D-arabinose oxidation was examined with growing cells and with the membrane fraction of G. suboxydans IFO 12528. 4-Keto-D-arabinose, the same intermediate as that from 2,5-diketo-D-gluconate, was detected, and it was oxidized to 4-keto-D-arabonate. Likewise, D-ribose was oxidized to 4-keto-D-ribose and then it was oxidized to 4-keto-D-ribonate. In addition to 4-keto-D-aldopentose 1-dehydrogenase, the presence of a novel membrane-bound enzyme, D-aldopentose 4-dehydrogenase, was confirmed in the membrane fraction. The formation of 4-keto-D-aldopentoses and 4-keto-D-pentonates (4-pentulosonates) was finally confirmed as reaction products of four different novel membrane-bound enzymes.
在我们之前的研究中，利用液化葡糖酸杆菌RCTMR 10鉴定出了一种从2,5-二酮-D-葡糖酸生成4-酮-D-阿拉伯糖酸的新微生物反应。该反应似乎同时发生了脱羧和脱氢。为了分析该反应的本质，我们对该微生物的膜部分进行了研究，并确认4-酮-D-阿拉伯糖是4-酮-D-阿拉伯糖酸的直接前体。该反应涉及两种新的膜结合酶，即2,5-二酮-D-葡糖酸脱羧酶和4-酮-D-醛戊糖1-脱氢酶。另外，D-阿拉伯糖酸被另一种膜结合酶D-阿拉伯糖酸4-脱氢酶氧化为4-酮-D-阿拉伯糖酸。更直接地，我们用生长中的细胞和氧化葡糖杆菌IFO 12528的膜部分研究了D-阿拉伯糖的氧化。检测到了与2,5-二酮-D-葡糖酸相同的中间体4-酮-D-阿拉伯糖，并且它被氧化为4-酮-D-阿拉伯糖酸。同样，D-核糖被氧化为4-酮-D-核糖，然后再被氧化为4-酮-D-核糖酸。除了4-酮-D-醛戊糖1-脱氢酶外，在膜部分还确认存在一种新的膜结合酶D-醛戊糖4-脱氢酶。最终确认4-酮-D-醛戊糖和4-酮-D-戊糖酸（4-戊酮糖酸）的形成是四种不同的新膜结合酶的反应产物。
