Formation of 4-keto-D-aldopentoses and 4-pentulosonates (4-keto-D-pentonates) with unidentified membrane-bound enzymes from acetic acid bacteria

ADACHI, O.; HOURS, R.A.; SHINAGAWA, E.; AKAKABE, Y.; YAKUSHI, T.; MATSUSHITA, K.

BIOSCIENCE, BIOTECHNOLOGY AND BIOCHEMISTRY

JAPAN SOC BIOSCI BIOTECHN AGROCHEM

Lugar: Tokyo; Año: 2011 vol. 75 p. 1801 - 1806

0916-8451

In our previous study, a new microbial reaction yielding 4-keto-D-arabonate from 2,5-diketo-D-gluconate was found with Gluconacetobacter liquefaciens RCTMR 10. It appeared that a decarboxylation and a dehydrogenation took place together in the reaction. To analyze the nature of the reaction, investigations were done with the membrane fraction of the organism. 4-Keto-D-arabinose was confirmed as the direct precursor for 4-keto-D-arabonate, when 2,5-diketo-D-gluconate was reacted with the membrane fraction. It was observed that 4-keto-D-arabinose was converted to 4-keto-D-arabonate. Existence of two novel membrane-bound enzymes corresponding to 2,5-diketo-D-gluconate decarboxylase and 4-keto-D-aldopentose 1-dehydrogenase were concerned in the reaction. Alternatively, D-arabonate was oxidized to 4-keto-D-arabonate by another membrane-bound enzyme, D-arabonate 4-dehydrogenase, which was found in most genera of Gluconobacter and Gluconacetobacter. 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 further converted to 4-keto-D-arabonate. Likewise, D-ribose was oxidized to 4-keto-D-ribose and then it was further oxidized to 4-keto-D-ribonate. In addition to 4-keto-D-aldopentose 1-dehydrogenase, existence of a novel membrane-bound enzyme, D-aldopentose 4-dehydrogenase, was confirmed in the membrane fraction. Formation of 4-keto-D-aldopentoses and 4-keto-D-aldopentonates (4-pentulosonates) was finally confirmed as the reaction products of the four different novel membrane-bound enzymes.