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The isolation and characterization of a uronic acid isomerase from F. heparinum is described. The enzyme converts glucuronic acid and galacturonic acid to fructuronic acid and tagaturonic acid. The equilibrium point of the reaction is affected by buffers. In the presence of borate, 75% of glucuronic acid is converted to fructuronic acid. In the presence of phosphate, the equilibrium is reached when 31% of glucuronic acid is converted to fructuronic acid. Conversely, fructuronic acid and tagaturonic acid are converted to glucuronic acid and galacturonic acid, respectively. Monosaccharides derived from heparin and chondroitin sulfates do not affect the activity of the isomerase, in contrast to the monosaccharides from hyaluronic acid which have marked inhibitory (or diluting) activity upon the enzyme. The role of this enzyme in the metabolism of mucopolysaccharides is discussed.

The effect of soil type on the uptake of dieldrin by wheat seedlings was studied using seven mineral soils containing 9 to 23 ppm of dieldrin. Although wheat seedlings grown in the sandy soils contained more dieldrin than those grown in the clay soils, there was no close relationship between sand, clay, or organic matter contents of the soils and the dieldrin contents of the plants. However, there was significant correlation between dieldrin uptake by wheat seedlings, the silt content of the soils, and the concentration of dieldrin in the soil water.