The ARG1 gene encodes arginase enzyme. This enzyme catalyzes the last step of the urea cycle, which is one of the metabolic pathways in the liver, where arginase is cytoplasmic. The metabolism of proteins in the diet creates nitrogen, as a waste product, in the circulatory system. The urea cycle processes this nitrogen, in the form of ammonia, from the blood, through a sequence of biochemical processes. Arginase is responsible for the incorporation of ammonia into urea, which can then be excreted from the body in urine. If urea cannot be synthesized, nitrogen accumulates in the blood and body tissues, as ammonia, which is a highly toxic substance, and may lead to brain damage and /or death. Arginase is also the enzyme necessary to regenerate the starting compound in the urea cycle, converting arginine to ornithine and beginning the cycle again.
In a 3-year-old male child with arginine deficiency, born to first-cousin parents, Kormal et al. (2004) identified a homozygosity for a deletion of 10,753 bp extending from the first intron to beyond the poly (A) site of the gene. The identification of the ARG1 deletion in this family enabled first-trimester prenatal diagnosis in a subsequent pregnancy.
Grody et al. (1992) explored the molecular pathology for liver arginase deficiency in a cohort that included a Saudi father and his child. In the child, loss of a TaqI cleavage site was identified in a homozygous state. Grody et al. (1992) speculated that this TaqI mutation lies outside exon 8 of the ARG1 gene.