L-Xylo-3-hexulose, a new rare sugar produced by the action of acetic acid bacteria on galactitol, an exception to Bertrand Hudson's rule

• Published in: Biochimica et biophysica acta. General subjects Vol. 1865; no. 1; p. 129740
• Main Authors: Xu, Yirong, Chi, Ping, Lv, Jiyang, Bilal, Muhammad, Cheng, Hairong
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.01.2021
• Subjects: acetic acid; Acetic Acid - metabolism; Bacterial Proteins - metabolism; Bertrand Hudson's rule; catalysts; Galactitol; Galactitol - metabolism; Gluconobacter; Gluconobacter - enzymology; Gluconobacter - metabolism; Gluconobacter cerinus; Gluconobacter oxydans; Hexoses - metabolism; Ketoses - metabolism; l-xylo-3-hexulose; oxidation; Oxidation-Reduction; oxidoreductases; Oxidoreductases - metabolism; PQQ Cofactor - metabolism; PQQ-dependent membrane-bound dehydrogenase; quinones; Rare sugars; Rare sugars; Bertrand Hudson's rule; PQQ-dependent membrane-bound dehydrogenase; Galactitol; Gluconobacter; l-xylo-3-hexulose
• ISSN: 0304-4165; 1872-8006; 1872-8006
• DOI: 10.1016/j.bbagen.2020.129740

In acetic acid bacteria such as Gluconobacter oxydans or Gluconobacter cerinus, pyrroloquinoline quinone (PQQ) in the periplasm serves as the redox cofactor for several membrane-bound dehydrogenases that oxidize polyhydric alcohols to rare sugars, which can be used as a healthy alternative for traditional sugars and sweeteners. These oxidation reactions obey the generally accepted Bertrand Hudson's rule, in which only the polyhydric alcohols that possess cis d-erythro hydroxyl groups can be oxidized to 2-ketoses using PQQ as a cofactor, while the polyhydric alcohols excluding cis d-erythro hydroxyl groups ruled out oxidation by PQQ-dependent membrane-bound dehydrogenases. Membrane fractions of G. oxydans were prepared and used as a cell-free catalyst to oxidize galactitol, with or without PQQ as a cofactor. In this study, we reported an interesting oxidation reaction that the polyhydric alcohols galactitol (dulcitol), which do not possess cis d-erythro hydroxyl groups, can be oxidized by PQQ-dependent membrane-bound dehydrogenase(s) of acetic acid bacteria at the C-3 and C-5 hydroxyl groups to produce rare sugars l-xylo-3-hexulose and d-tagatose. This reaction may represent an exception to Bertrand Hudson's rule. Bertrand Hudson's rule is a well-known theory in polyhydric alcohols oxidation by PQQ-dependent membrane-bound dehydrogenase in acetic acid bacteria. In this study, galactitol oxidation by a PQQ-dependent membrane-bound dehydrogenase represents an exception to the Bertrand Hudson's rule. Further identification of the associated enzymes and deciphering the explicit enzymatic mechanism will prove this theory. Bertrand Hudson's rule is a well-known theory in polyhydric alcohols oxidation by PQQ-dependent membrane-bound dehydrogenase in acetic acid bacteria such as Gluconobacter oxydans. In this study, we found that galactitol, without cis-d-erythro configuration, can also be oxidized by a PQQ-dependent membrane-bound dehydrogenase, represents an exception to the well-known Bertrand Hudson's rule. [Display omitted] •Galactitol can be oxidized by PQQ-dependent membrane-bound dehydrogenase of Gluconobacter strains and does not conform to well-known Bertrand-Hudson's rule.•The oxidized positions were proved to be at the C-3 and C-5 hydroxyl groups of galactitol to produce rare sugars l-xylo-3-hexulose and d-tagatose.•This reaction may represent an exception to Bertrand Hudson's rule.