Pantothenate biosynthesis in higher plants: advances and challenges

Pantothenate (vitamin B-5) is the precursor of the 4'-phosphopantetheine moiety of coenzyme A and acyl-carrier protein. Plants and microorganisms make the vitamin de novo, whereas animals must obtain it from their diet. Pantothenate is produced commercially by chemical synthesis for vitamin supplements, feed additives and cosmetics. An attractive alternative for production is biotransformation, which would avoid expensive procedures for separation of racemic intermediates. The biosynthetic pathway in bacteria, comprising four enzymic reactions, is well-established, and enzymes from Escherichia coli have been fully characterized including the overexpression and purification of recombinant enzymes and the determination of their X-ray crystal structures. Pantothenate biosynthesis in higher plants is beginning to be elucidated, and genes encoding the first and last enzymes have been identified and characterized in Arabidopsis thaliana and Oryza sativa (rice). This review describes our current understanding of the pathway in plants and the challenges that lie ahead in engineering plants to make increased amounts of the vitamin.