Triphosphate is a salt or ester containing three phosphate groups. It is the ionic form of triphosphoric acid, a condensed form of phosphoric acid. Triphosphate is an intermediate in the biosynthesis of folate, the metabolism of purine, the metabolism of porphyrin and chlorophyll, the metabolism of pyrimidine, and the metabolism of thiamine. It is a substrate for transforming protein p21/H-Ras-1, bis(5'-adenosyl)-triphosphatase, ectonucleoside triphosphate diphosphohydrolase, DNA polymerase gamma subunit 1, DNA nucleotidylexotransferase, inosine triphosphate pyrophosphatase, cob(I)yrinic acid a,c-diamide adenosyltransferase (mitochondrial), thiamine-triphosphatase, DNA-directed RNA polymerase III 32 kDa polypeptide, and 6-pyruvoyl tetrahydrobiopterin synthase. Compounds such as ATP (adenosine triphosphate) are esters of triphosphoric acid. Polyphosphates are hydrolyzed into smaller units (orthophosphates) in the gut before absorption, which may induce metabolic acidosis. The acute toxicity of polyphosphonates is low as the lowest LD50 after oral administration is > 1,000 mg/kg body weight. Polyphosphates are moderately irritating to skin and mucous membrane because of their alkalinity. No mutagenic potential was observed when TTP was tested in a Salmonella/microsome assay (Ames test) and in a chromosomal aberration assay in vitro using a Chinese hamster fibroblast cell line (Ishidate et al. 1984). Tetrasodium pyrophosphate was not mutagenic in an in vitro assay using S. cerevisiae strains and S. typhimurium strains with and without the addition of mammalian metabolic activation preparations (IPCS 1982). Reproduction studies in three generations of rats on diets with 0.5% TTP were performed. TTP had no effects on fertility or litter size, or on growth or survival on offspring (Hodge 1964).