INDUCIBLE UDP-GLUCOSE DEHYDROGENASE FROM FRENCH BEAN (PHASEOLUS-VULGARIS L) LOCATES TO VASCULAR TISSUE AND HAS ALCOHOL-DEHYDROGENASE ACTIVITY

UDP-glucose dehydrogenase is responsible for channelling UDP-glucose i nto the pool of UDP-sugars utilized in the synthesis of wall matrix po lysaccharides and glycoproteins. It has been purified to homogeneity f rom suspension-cultured cells of French bean by a combination of hydro phobic-interaction chromatography, gel filtration and dye-ligand chrom atography. The enzyme had a subunit of M(r) 40 000. K-m values were me asured for UDP-glucose as 5.5 +/- 1.4 mM and for NAD(+) as 20 +/- 3 mu M. It was subject to inhibition by UDP-xylose. UDP-glucose dehydrogen ase activity co-purified with alcohol dehydrogenase activity from susp ension-cultured cells, elicitor-treated cells and elongating hypocotyl s, even when many additional chromatographic steps were employed subse quently. The protein from each source was resolved into virtually iden tical patterns of isoforms on two-dimensional isoelectric focusing/PAG E. However, a combination of peptide mapping and sequence analysis, ge l analysis using activity staining and kinetic analysis suggests that both activities are a function of the same protein. An antibody was ra ised and used to immunolocalize UDP-glucose dehydrogenase to developin g xylem and phloem of French bean hypocotyl. Together with data publis hed previously, these results are consistent with an important role in the regulation of carbon flux into wall matrix polysaccharides.