“…Later, Saheki et al (1980Saheki et al ( , 1981 reported that the enzyme abnormalities of citrullinemia can be classified as qualitative (type I) or quantitative (type II), and that in type I, ASS is affected not only in the liver but also in the kidney and in cultured fibroblast cells, and is kinetically abnormal, while in type II, ASS is affected only in the liver (Saheki et al 1982(Saheki et al , 1983a, where it is deficient but kinetically normal and has the same specific activity as the control. Further research showed that type I citrullinemia, together with type III, in which ASS is almost completely absent in every cell where the ASS gene is expressed (Saheki et al 1985a(Saheki et al , 1987aImamura et al 1987), is caused by mutations in the ASS gene (Kobayashi et al , 1990(Kobayashi et al , 1991(Kobayashi et al , 1994(Kobayashi et al , 1995aKakinoki et al 1997;Vilaseca et al 2001). Kinetically abnormal mutant ASS is found in patients with type I citrullinemia, and mainly splicing mutations, but not missense mutations, cause type III citrullinemia (Kobayashi et al , 1994(Kobayashi et al , 1995a.…”