The urea cycle functions to incorporate ammonia. generated by normal metabolism. into urea. Urea cycle disorders (UCDs) are caused by loss of function in any of the enzymes responsible for ureagenesis. https://www.nacrack.com/super-save-2001-2004-LEXUS-LS430-Sedan-Rear-Bumper-Cover-w-o-Park-Assist-Paint-Code-3P2-hot-choice/