InterPro domain: IPR006390

This domain is present in sequences representing dihydropteroate synthase, the enzyme that catalyzes the second to last step in folic acid biosynthesis.

Dihydropteroate synthase ( 2.5.1.15 ) (DHPS), a functional homodimer, catalyses the condensation of 6-hydroxymethyl-7,8-dihydropteridine pyrophosphate to para-aminobenzoic acid to form 7,8-dihydropteroate. This is the second step in the three-step pathway leading from 6-hydroxymethyl-7,8-dihydropterin to 7,8-dihydrofolate. DHPS is the target of sulfonamides, which are substrate analogues that compete with para-aminobenzoic acid. Bacterial DHPS (gene sul or folP) [ 1 ] is a protein of about 275 to 315 amino acid residues that is either chromosomally encoded or found on various antibiotic resistance plasmids. In the lower eukaryote Pneumocystis carinii, DHPS is the C-terminal domain of a multifunctional folate synthesis enzyme (gene fas) [ 2 ].

Prokaryotes (and some lower eukaryotes) must synthesize folate de novo, while higher eukaryotes are able to utilize dietary folate and therefore lack DHPS.

1. An apparent Bacillus subtilis folic acid biosynthetic operon containing pab, an amphibolic trpG gene, a third gene required for synthesis of para-aminobenzoic acid, and the dihydropteroate synthase gene. J. Bacteriol. 172, 7211-26
2. The multifunctional folic acid synthesis fas gene of Pneumocystis carinii appears to encode dihydropteroate synthase and hydroxymethyldihydropterin pyrophosphokinase. Gene 112, 213-8