Folic acid deaminase activity during development in Dictyostelium discoideum.
Folic acid attracts vegetative amoebae of Dictyostelium discoideum. Secreted by bacteria, it may act as a food-seeking device. The inactivation of this attractant is catalyzed by a deaminase. As assay has been developed to measure the folic acid deaminase activity. In addition to cell-surface an intracellular deaminase, the amoebae of D. discoideum release the enzyme into the medium. The pH optimum of the extracellular enzyme was 6.0, and higher for the cell-associated deaminases. The extracellular enzyme was secreted maximally by vegetative amoebae, and its activity diminished during cell differentiation. The cell-surface bound enzyme was less active than the extracellular enzyme, and its activity decreased twofold during a 6-h starvation period. The enzyme activity of homogenates and 48,000 x g pellets diminished during this period 35 to 40%. The supernatant of a homogenate had a higher deaminase activity than the homogenate itself or its pellet; this suggests the presence of an inhibitor in the particulate fraction. The underlying mechanism for inactivation of folic acid has similar characteristics as that for inactivation of cyclic adenosine monophosphate.
D000619:Aminohydrolases / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology; D004023:Dictyostelium / Q000201:enzymology* / Q000254:growth & development; D005492:Folic Acid / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D015800:Protozoan Proteins; D011622:Pterins / Q000378:metabolism; D013379:Substrate Specificity; D013696:Temperature
D015800:Protozoan Proteins; D011622:Pterins; D005492:Folic Acid; D000619:Aminohydrolases; C020144:folic acid deaminase, Dictyostelium discoideum