ENZYMATIC CONVERSION OF PHENYLPYRUVATE TO PHENYLACETATE

Using Acromobacter eurydice isolated from soil, we clarified the pathway by which phenylpyruvate is metabolized to phenylacetate through phenylacetaldehyde. We defined the enzymes concerned as phenylpyruvate decarboxylase and phenylacetaldehyde dehydrogenase. Phenylpyruvate decarboxylase was purified and some of its properties were studied. It catalyzed the non-oxidative decarboxylation of phenylpyruvate in which diphosphothiamin (DPT) and Mg2+ were cofactors. Compounds such as phenylpyruvate, indolepyruvate and α-keto acids with more than 6 carbons atoms in a straight chain served as substrates for the decarboxylase. Phenylacetaldehyde dehydrogenase required NAD as cofactor. To determine the amount of phenylacetaldehyde produced in the enzymic reaction, its 2,4-dinitrophenyl (DNP)-hydrazone was extracted with xylene at 70° and color was developed with NaOH-ethanol. When the bacterial cells were grown on tryptophan, both the decarboxylase and the dehydrogenase were found in the extract. In these cells tryptophan was metabolize to indoleacetate through indoleprruvate and indoleacetaldehyde. © 1968.