ORC2 and ornithine translocase deficiency: This is catalyzed either by ORC2 [68] or by the SLC25A29 gene product (previously reported to be a mitochondrial carnitine/acylcarnitine- or ornithine-like carrier called ORNT3 [69]), which is able to rescue the ornithine metabolism deficiency in fibroblasts of HHH patients [69,70] and to transport basic amino acids as well as ornithine into proteoliposomes [71].