Lastly, human mutations in SLC6A20, encoding the SLC6A20 protein that can mediate proline transport, have been linked to complex digenic iminoglycinuria (a renal disorder with impaired reabsorption of glycine and imino acids [proline and hydroxyproline]) and hyperglycinuria (Broer et al, 2008). This evidence concerns the gene SLC6A20 and iminoglycinuria.