ASS1 and autosomal dominant polycystic kidney disease: Another study showed that the expression of ASS1, an enzyme that converts aspartate to argininosuccinate, which is needed for arginine production, is reduced in murine and human ADPKD, and that arginine depletion results in a dose-dependent compensatory increase in ASS1 levels as well as decreased cystogenesis in vitro and ex vivo with minimal toxicity to normal cells16.