Purification and cDNA cloning of UDP-D-glucuronate carboxy-lyase (UDP-D-xylose synthase) from pea [Pisum sativm] seedlings

Uridine diphospho-d-glucuronate carboxy-lyase (UDP-d-xylose synthase; EC 4.1.1.35), which catalyzes the conversion of UDP-d-glucuronate to UDP-d-xylose, was purified to apparent homogenity from pea (Pisum sativum L.) seedlings. The pH optimum for enzyme activity was around 5–6, and the activity was not affected by exogeneously supplied NAD+ and NADH. The purified enzyme had a molecular weight of 250 kDa and consisted of 42 kDa polypeptides. Based on the amino acid sequence, a probe (400 bp) was prepared with degenerate primers by a reverse transcriptase-PCR. Using this probe, a clone encoding 346 amino acid residues was screened from a pea cDNA library. The recombinant protein expressed in Escherichia coli catalyzed conversion of UDP-d-glucuronate to UDP-d-xylose, confirming that the isolated clone encoded UDP-d-glucuronate carboxy-lyase.