Vitamin B5: Pantothenate

Abstract

Vitamin B5 is the simple acid pantothenic acid (from the Greek pantos, meaning widespread). B5 needs to undergo five enzymatic steps to be converted to coenzyme A, in which the terminal thiol of a cysteamine moiety is the key reactive atom, once dissociated to the thiolate anion. The thiolate serves as nucleophile towards a variety of acids to yield acyl thioesters (acyl-CoAs). These are the cellular acylating agents in metabolic pathways. The two-carbon acyl group in acetyl CoA is doubly activated: as electrophile at C1 and as nucleophile at C2, and so ideally set up for C–C bond formations in fatty acid and steroid biosynthetic pathways, as well as the first step in the citrate metabolic cycle.