English: Biosynthesis of pantothenic acid (vitamin B5). B5 is shown as pantothenate (anion).¹

This route is followed by most bacteria like Escherichia coli, Salmonella typhimurium and Corynebacterium glutamicum. Importance of the routes may vary. E.g.: in S. typhimurium most of the α-ketoisovalerate is provided by dihydroxy-acid dehydratase.¹

Most plants and archaea follow a very similar route, and make B5 by joining pantoate and β-alanine.²

α-ketoisovalerate can revert back to valine and vice versa.¹

All of the BCAT and valine-pyruvate transaminase substrates are not shown.

EC numbers are:

• 4.2.1.9 dihydroxy-acid dehydratase
• 2.6.1.42 BCAT (Branched-chain-amino-acid transaminase)
• 2.6.1.66 valine—pyruvate transaminase
• 2.1.2.11 ketopantoate hydroxymethyltransferase
• 1.1.1.169 ketopantoate reductase
• 1.1.1.86 ketol-acid reductoisomerase
• 4.1.1.11 aspartate 1-decarboxylase
• 6.3.2.1 pantothenate synthase

Sources:

• 1. Leonardi, R; Jackowski, S (2007). "Biosynthesis of Pantothenic Acid and Coenzyme A". EcoSal Plus. 2 (2). doi:10.1128/ecosalplus.3.6.3.4. ISSN 2324-6200.
• 2. Handbook of vitamins. Zempleni, J et al (4th ed.). Taylor & Francis. 2007. pp. 290–291. ISBN 9780849340222