Competitive inhibition for amino acid uptake by the indigenous microflora of Upper Klamath Lake.

The uptake of a specific (14)C-amino acid by the heterotrophic microorganisms in the epilimnion of an eutrophic lake was influenced by the presence of other amino acids. The effect of unlabeled serine on (14)C-glycine uptake was shown to be caused by competitive inhibition, which changed the interpretation of the kinetic parameters, the turnover time, T(t), and the sum of a transport constant, (K(t) + (S(n)), and the natural substrate concentration. The maximum velocity of uptake, V(max), is unaffected by the competitive inhibition.