CAD protein
protein-coding gene in the species Homo sapiens
CAD protein (carbamoyl-phosphate synthetase 2, aspartate transcarbamylase, and dihydroorotase) is a trifunctional multi-domain enzyme involved in the first three steps of pyrimidine biosynthesis. De-novo synthesis starts with cytosolic carbamoylphosphate synthetase II which uses glutamine, carbon dioxide and ATP. This enzyme is inhibited by uridine triphosphate (feedback inhibition).
In 2015, the first observed pathological mutations of CAD were found in a four-year-old boy.
CAD protein has been observed in the mid-piece of mammalian spermatozoa, among the mitochondria.
Structure
CAD protein has a molecular weight of 243 KDa. It is a polypeptide made up of four different domains which make for a multi enzyme unit: Glutaminase (GLN), carbamoyl phosphate synthetase (CPS II), Dihydroorotase (DHO) and aspartate transcarbamoylase (ATC). The protein assembles into ~1.5MDa hexamers. More specifically, the DHO domain assembles into dimers, and ATC domains do so into trimers. The hexamers are then formed by DHO dimerization of two ATC trimers, and this connection does not impact the kinetic properties. In addition, it is thought that three GLN-CPS II dimers border the DHO-ATC complex.
The public source identifies “CAD protein” as protein-coding gene in the species Homo sapiens. This brief keeps that definition visible, then builds a research path around protein, protein-coding and gene.
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The date and method of observation matter as much as the stated conclusion, especially where classification or consensus has changed. The source revision retrieved here is dated Aug 11, 2026. The linked authority identifier is Q17855283. None of the 0 selected statements returned an explicit reference. The first chronological checks are 2015.
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This entry incorporates text from “CAD protein” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.