Transporter that mediates resorption of neutral amino acids across the apical membrane of renal and intestinal epithelial cells (PubMed:18424768, PubMed:17167413, PubMed:26240152, PubMed:19185582, PubMed:15044460). This uptake is sodium-dependent and chloride-independent (PubMed:18424768, PubMed:19185582, PubMed:15044460, PubMed:21636576, PubMed:26240152). Requires CLTRN in kidney or ACE2 in intestine for cell surface expression and amino acid transporter activity (PubMed:18424768, PubMed:17167413, PubMed:19185582, PubMed:22677001). L-alanine(in) + Na(+)(in) = L-alanine(out) + Na(+)(out) L-cysteine(in) + Na(+)(in) = L-cysteine(out) + Na(+)(out) L-glutamine(in) + Na(+)(in) = L-glutamine(out) + Na(+)(out) glycine(in) + Na(+)(in) = glycine(out) + Na(+)(out) L-isoleucine(in) + Na(+)(in) = L-isoleucine(out) + Na(+)(out) L-leucine(in) + Na(+)(in) = L-leucine(out) + Na(+)(out) L-methionine(in) + Na(+)(in) = L-methionine(out) + Na(+)(out) L-phenylalanine(in) + Na(+)(in) = L-phenylalanine(out) + Na(+)(out) L-serine(in) + Na(+)(in) = L-serine(out) + Na(+)(out) L-tryptophan(in) + Na(+)(in) = L-tryptophan(out) + Na(+)(out) L-tyrosine(in) + Na(+)(in) = L-tyrosine(out) + Na(+)(out) L-valine(in) + Na(+)(in) = L-valine(out) + Na(+)(out) Vmax for leucine is about twice the value of Vmax for glutamine, and three times the value of Vmax for phenylalanine. KM and Vmax values are complex functions of the concentration of substrate (L-amino acid) and cosubstrate (Na(+)) and the membrane potential. Interacts in a tissue-specific manner with ACE2 in small intestine and with CLTRN in the kidney (PubMed:19185582, PubMed:17167413). Interacts with CLTRN; this interaction is required for trafficking of SLC6A19 to the plasma membrane and for its catalytic activation in kidneys (PubMed:17167413). Interacts with ACE2; this interaction is required for trafficking of SLC6A19 to the plasma membrane and for its catalytic activation in intestine (PubMed:19185582). Interacts with ANPEP; the interaction positively regulates its amino acid transporter activity (PubMed:22677001). Localizes in small intestine brush border membranes (at protein level). Predominantly expressed in kidney and small intestine (at protein level) (PubMed:15044460, PubMed:19185582). Expressed in the intestinal brush border (at protein level) (PubMed:22677001). Expression not observed in other organs, such as lung, skeletal muscle, brain, liver and pancreas. In kidney, expression is localized in the renal cortex but not in the medulla. Substantial amounts of expression in the proximal tubules. The distal nephron segments and the glomeruli are consistently negative. In the small intestine, expression is exclusively localized in villus enterocytes. High resolution of the hybridization-positive villi reveals a gradient of expression with the highest levels in apical cells. Not detected in crypt cells or in any other cell types of the small intestine. Deficient mice exhibit reduced growth, impaired body weight control, insulin response and amino acid absorption and excretion. Belongs to the sodium:neurotransmitter symporter (SNF) (TC 2.A.22) family. SLC6A19 subfamily.