The enzymatic conversion of mandelic acid to benzoic acid. II. Properties of the particulate fractions.

Mandelic acid can serve as sole source of carbon and energy for the growth of certain strains of Pseudomonas fluorescens. Analysis of the enzymatic patterns of cells grown on various substrates (Stanier, 1947, 1948; Sleeper and Stanier, 1950) has led to formulation of the following sequence for the initial steps in its diimilation: Mandelic acid -b benzoylformic acid -. benzaldehyde -* benzoic acid -catechol. All the relevant enzymes are substrate induced. Living cells consume approximately 11 atoms of oxygen per mole of mandelate oxidized with an R.Q. of slightly less than one. After slow vacuum drying, mandelate grown cells yield preparations which consume only two atoms of oxygen per mole of mandelate-sufficient for oxidation to benzoic acid (Sleeper, Tsuchida, and Stanier, 1950). Cells harvested from a medium which contains sodium DL-mandelate, or dried cells prepared from them, oxidize both isomers at equal rate. In this work the series of enzymes which convert DL-mandelic acid to benzoic acid has been separated and some of their properties determined. In this paper the properties of the overall system, together with the primary separation of the relevant enzymes into particulate and soluble fractions, are reported. The properties of the particle fractions are described in paper two of the series (Stanier et al., 1953), and the further fractionation and characterization of the soluble enzymes, in paper three (Gunsalus et al., 1953).