Sugar nucleotides, the activated forms of monosaccharides, are used as donor substrates by glycosyltransferases in the in vivo biosynthesis of polysaccharides, proteoglycans and glycoglycerolipids. In mammals, uridine 5'-diphosphate-glucose (UDP-Glc) and uridine 5'-diphosphate-glucuronic acid (UDP-GlcA) are common building blocks of glycans and glycoconjugates. The commercial demand for these high-energy donors is increasing, while the understanding and application of enzymatic glycan synthesis has leapt forward in recent years. To produce valuable UDP-GlcA in a cost-effective way, here, UDP-sugar pyrophosphorylase from Arabidopsis thaliana was constitutively expressed in Pichia pastoris and secreted into the extracellular medium. Under these conditions, the synthesis of 4.2 g UDP-GlcA or 5.5 g UDP-Glc per liter of culture was revealed in the culture medium, without any need for purification. An anion exchange chromatography purification method for UDP-sugars was also developed. This route opens a door to large-scale production of the cheaper UDP-GlcA.