Uptake of L-valine and other amino acids by the polychaete Nereis virens

Abstract

For valine uptake by the polychaete Nereis virens Sars, the kinetic constants were: Vmax=355 nmol g-1 fresh weight h-1, Km=20 μM. Leucine and some other amino acids acted as partial inhibitors of valine uptake. Valine uptake rate was 78% higher at 21.5‰ S than at 14‰ S. The major portion of valine absorbed by the polychaete could be extracted as free valine, with 6.5 to 15.6% being respired, and 3.6 to 9.5% incorporated into proteins. Calculations indicate that 7 to 12% of the metabolism of N. virens may be sustained by uptake of glycine and aspartic acid from natural concentrations. It is suggested that uptake of amino acids by this worm is important in the nitrogen cycling of marine sediments.