Pteroates

Pteroates are a class of pteridine-based compounds that form the core moiety of folate molecules in many microorganisms, plants, and some fungi. The term typically refers to dihydropteroate and related derivatives that combine a pterin-derived ring system with a para-aminobenzoic acid (PABA) unit. This pteroate backbone is the essential precursor to folates, which are further elaborated by the addition of glutamate residues and reduction to the active folate cofactors.

Chemically, a pteroate consists of a pteridine ring linked to PABA. In biosynthetic pathways, dihydropterin pyrophosphate condenses with PABA to form dihydropteroate. Through subsequent enzymatic steps, dihydropteroate is converted to dihydrofolate and, with further reduction and polyglutamation, to tetrahydrofolate (THF), the usable form of folate required for one-carbon transfer reactions in thymidylate and purine synthesis.

Biological role and distribution: Pteroates themselves are not the end cofactors; they are key intermediates in the de novo synthesis of folates in bacteria, plants, and some fungi. Humans do not synthesize folates de novo and obtain them through diet; nevertheless, pteroate metabolism in microbes is critical for their growth and replication, making the pteroate pathway a notable target in antimicrobial strategies.

Medical relevance: The bacterial enzyme dihydropteroate synthase (DHPS) catalyzes the formation of dihydropteroate from dihydropterin pyrophosphate and PABA. Sulfonamide antibiotics act as competitive inhibitors of DHPS, blocking folate synthesis in susceptible microbes. This mechanism underpins the antimicrobial action and the potential for resistance through mutations or metabolic bypass.