Uptake of amino acids by the mussel Modiolus demissus

Unidirectional and net fluxes of amino acids into isolated gills and intact specimens of the mussel Modiolus demissus were studied. Influx follows Michaelis‐Menten type kinetics, with Kt = 19 and 21 μM, and Vmax = 47 and 107 μmoles/g‐hr for cycloleucine and glycine, respectively. The transport mechanism is specific for neutral amino acids, although other transport systems apparently exist for acidic and basic amino acids. Measurements of primary amines in interstitial waters from the sediments where the animals were found showed that variations in the concentration are found with depth in the sediment, with a maximal concentration of 110 μM. The major primary amines were identified as amino acids. Isolated gills were shown to deplete the medium of the naturally occurring primary amines.