The Metabolism of Tartaric Acid by a Pseudomonas. a New Pathway.

Many micro-organisms can utilize tartaric acid for growth. The only well-established reaction sequence for its dissimilation is that first proposed by Barker (1936) for the breakdown of (+ )-tartaric acid by Aerobacter aerogenre in which oxaloacetic and pyruvic acids are formed. By this sequence, tartrate is dehydrated to oxaloacetate, which in turn is usually decomposed so rapidly to pyruvate that it is difficult to isolate any oxaloacetate produced by the action of the dehydratase. Only Shilo (1957), who used EDTA to inhibit oxaloacetate decarboxylase in cell-free extracts of tartrate-grown Pseudomona8 species, has reported the formation of oxaloacetate in good yields; this was made the basis of an assay of tartrate dehydratase. In the present investigation we used a species of PWeudomonas which, in contrast with those studied previously, contained no more oxaloacetate decarboxylase when grown with tartrate than when grown with other compounds as sole sources of carbon. This organism, which converts glycine into glycerate (Dagley, Trudgill & Callely, 1961), appears to metabolize (+ )-tartrate by a reaction sequence in which decarboxylation to give glycerate precedes the removal ofwater so that oxaloacetate is not a reaction intermediate: after phosphorylation, glycerate is converted into pyruvate by enzymes common to glycolysis. A brief account of some of this work has already appeared (Dagley & Trudgill, 1962).