Neutral D-amino Acids Research Articles

A common step in the intestinal absorption mechanisms of d- and l-methionine

1. 1. The intestinal absorption of d- and l-methionine in the chicken has been shown to occur by attachment to a common l-preferring site presumably on the mucosal epithelial membrane. The possibility of separate binding sites with overlapping specificities for these isomers has been ruled out by a kinetic test. 2. 2. An equation of uptake of sugars at the steady state in bacteria was used to study uptake in intestinal segments. 3. 3. Affinity constants for inhibitors ( K i ) were determined from plots of reciprocal per cent inhibition versus reciprocal inhibitor concentration. 4. 4. Neutral amino acids of the l-configuration had high affinity for the methionine transport site, while neutral d-amino acids, and except for d-methionine had very low affinity. 5. 5. l-Lysine, l-histidine and l-aspartic acid had very poor affinity for this site, while d-aspartic acid had no affinity, d-Histidine caused stimulation of l-methionine uptake.