Mediates the calcium-dependent uptake of imino acids such as L-proline, N-methyl-L-proline and pipecolate as well as N-methylated amino acids. Located in the apical brush border membrane of kidney proximal tubule cells and in the apical membrane of enterocytes lining the intestinal villi. Expressed in brain, kidney, small intestine, thymus, spleen and lung. In the brain, expressed in cerebellum, cortex and brain stem. Not detected in liver, muscle or heart. Belongs to the sodium:neurotransmitter symporter (SNF) (TC 2.A.22) family. SLC6A20 subfamily.