Pyrimidine metabolism end product

Unlike the low solubility products of purine catabolism, catabolism of the pyrimidines forms highly water-soluble products-- CO2, NH3, b-alanine, and b-aminoisobutyrate (Figure 33-12). Humans transaminate b-aminoisobutyrate to methylmalonate semialdehyde, which then forms succinyl-CoA (see Figure 19-2). Excretion of b-aminoisobutyrate increases in leukemia and severe x-ray radiation exposure due to increased destruction of DNA. However, many persons of Chinese or Japanese ancestry routinely excrete b-aminoisobutyrate.Ref: Harpers Illustrated Biochemistry, 30th edition, page no: 355