Electrogenic proton/amino acid symporter with a high selectivity for the small side chains amino acids glycine, alanine and proline, where both L- and D-enantiomers are transported. Extension of the backbone length, as in beta-alanine and 4-aminobutanoate or methylation of the amino group, as in sarcosine and N,N- dimethylglycine, are also tolerated but decrease transport efficiency. A free carboxyl group is preferred. {ECO:0000269|PubMed:12809675, ECO:0000269|PubMed:19033659}. This is the function of SLC36A2 (solute carrier family 36 member 2, Ensembl gene identifier ENSG00000186335).