Members of this protein family appear to represent a novel form of phosphoribosylaminoimidazole-succinocarboxamide synthase (SAICAR synthetase), significantly different in sequence from (IPR001636), which is found in a broad range of bacteria and eukaryotes. Members of this family are found within the gammaproteobacteria in the genera Vibrio, Shewanella, and Colwellia, and also (reported as a fragment) in the primitive eukaryote Guillardia theta (Cryptomonas phi).