CAD protein, also known as carbamoyl-phosphate synthetase 2, aspartate transcarbamoylase, and dihydroorotase, is a multifunctional enzyme complex that catalyzes the first three steps in the de novo synthesis of pyrimidine nucleotides. This process is crucial for the production of nucleic acids, active intermediates, and cell membranes, and plays a key role in cellular and organismal physiology. CAD is regulated by various pathways, including the mitogen-activated protein kinase (MAPK) cascade, and its dysregulation can lead to diseases such as cancer and neurological disorders.