A novel chemotaxis regulating enzyme that splits folic acid into 6-hydroxymethylpterin and P-aminobenzoylgutamic acid.

After sta~ation, amoebae of the cellular slime molds secrete acrasin [l] by which they attract each other and form an aggregate that differentiates into stalk cells and spores. In a favourable environment spores germinate yielding amoebae which feed on bacteria and m~tiply. Vegetative amoebae are also sensitive to chemotactic stimuli [4,6], which differ from acrasins. They are attracted to bacteria, which apparently secrete chemoattractants for amoebae [2,3]. Folic acid was reported a chemoattractant for vegetative amoebae of the cellular slime molds [4]. Folic acid is also, although less ~hemotactic~y active in the aggregative stage except in D~c~oste~~um discoideum [5,7 J. The function of folic acid in the cellular slime molds is thought to be a signal for food detection [4,7]. The inactivation of the chemotactic signal is regulated by enzymatic degradation. One way to inactivate folic acid is by folic acid deaminase, as studied in D. discoideum and Po~ys~hondyZium violaceum [8,9]. We examined the chemotactic activity of the deaminated folic acid in several species of the cellular slime molds and discovered that in some species the ehemotactic activity is not lost by deamination. This indicates that another chemotactic regulator enzyme exists. Folic acid metabolism has been