The stereochemistry of an enzymatic reaction; the oxidation of 1-, d-, and epi-inositol by Acetobacter suboxydans.

The property of certain members of the group of acetic acid bacteria (1) that brings about the incomplete oxidation of various substrates, stopping often at the primary oxidation product, is emphasized in the name of the bacterial type with which this paper deals, Acetobacter mboxydans (2). The action of this organism on polyhydroxy compounds terminates, as a rule, with the formation of a monoketo compound. Certain sterical limitations, observed experimentally, have found their expression in the well known rule of Bertrand (3) which, however, does not apply to all substrates C&4). It occurred to us that the stereochemical specificity of this interesting enzyme system could be defined with greater precision if a stereoisomeric series of cyclic polyhydroxy compounds were employed as the substrates of oxidation, since in this case the lack of free rotation around carbon to carbon bonds should permit a clearer correlation between reactivity and the spatial arrangement of the reactive groups. For this purpose, several isomers of the inositol group and related cyclitols were chosen. The oxidation rates were studied manometrically and whenever possible the oxidation products isolated and identified. The experiments, which in part have been presented very briefly in a preliminary communication (5), were carried out with resting cells.’ Since the localization of the enzyme system within the bacterial cell is unknown, it is not yet possible to present an adequate discussion of the reasons for the differences in oxidation rates found for the several stereoisomers. Should the speed of permeation of the substrate into the cell prove to be the ratedetermining step, then it would become necessary to consider the bacterial