Family member FomD is a protein encoded in the fosfomycin biosynthesis gene cluster [1,2], which hydrolyses (S)-HPP-CMP to give (S)-HPP and CMP in the presence of Mn2 or Co2 [2]. FomD also hydrolyses cytidylyl 2-hydroxyethylphosphonate (HEP-CMP), which is a biosynthetic intermediate before C-methylation. FomD structure revealed that it has a beta-barrel fold consisting of a large twisted antiparallel beta-sheet, a key feature of DUF402-containing proteins. The function of this domain is unknown. It has a Tyr residue which activates a water molecule to promote nucleophilic attack on the phosphorus atom of the phosphonate moiety [2]. This domain has also been found in Ntdp (nucleoside tri- and diphosphatase, also known as Sa1684) from Staphylococcus aureus [3].

1: Cloning and nucleotide sequence of fosfomycin biosynthetic genes of Streptomyces wedmorensis. Hidaka T, Goda M, Kuzuyama T, Takei N, Hidaka M, Seto H; Mol Gen Genet 1995;249:274-280. PMID:7500951

2: Biochemical and Structural Analysis of FomD That Catalyzes the Hydrolysis of Cytidylyl ( S)-2-Hydroxypropylphosphonate in Fosfomycin Biosynthesis. Sato S, Miyanaga A, Kim SY, Kuzuyama T, Kudo F, Eguchi T; Biochemistry. 2018;57:4858-4866. PMID:30010320

3: The structural mechanism for the nucleoside tri- and diphosphate hydrolysis activity of Ntdp from Staphylococcus aureus. Wang Z, Shen H, He B, Teng M, Guo Q, Li X; FEBS J. 2021;288:6019-6034. PMID:33955674