A member of the class of phosphonic acids that is phosphonic acid in which the hydrogen attached to the phosphorous is replaced by a carboxymethyl group. ChEBI: Phosphonoacetic acid is a member of the class of phosphonic acids that is phosphonic acid in which the hydrogen attached to the phosphorous is replaced by a carboxymethyl group. It has a role as an antiviral agent and an EC 2.7.7.7 (DNA-directed DNA polymerase) inhibitor. It is a monocarboxylic acid and a member of phosphonic acids. It is functionally related to a phosphonic acid and an acetic acid. It is a conjugate acid of a hydrogen phosphonatoacetate(2-).