Extracellular folate deaminase of Dictyostelium discoideum

Folate deaminase released from cells of Dictyostelium discoideum is heterogeneous with respect to molecular weight and stability at 60 degrees C. The most heat-stable component isoelectrofocuses in a broad band at approx. pH 6. The Km value of this component for folate is approx. 7 x 10(-7)M and Mr approx. 40 000. The major portion if not all of the deaminase binds to immobilized concanavalin A and lentil lectin. Extracellular folate deaminase has a pH-optimum of approx. pH 6.0. This is higher than that of lysosomal enzymes, which are also glycoproteins released into the extracellular medium.