Submitted to: Annual Missouri Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 4/1/2005
Publication Date: 4/27/2005
Citation: Litterer, L.A., Plaisance, K.L., Schnurr, J.A., Storey, K.K., Gronwald, J.W., Somers, D.A. 2005. Characterization of Arabidopsis UDP-sugar pyrophosphorylase [abstract]. 22nd Annual Missouri Symposium. Genomics and Beyond: Frontiers in Plant Biology. p. 79. Interpretive Summary:
Technical Abstract: UDP-sugars are critical substrates for synthesis of cell wall polysaccharides in plants. We used a bioinformatics approach to clone and characterize an UDP-sugar pyrophosphorylase from Arabidopsis thaliana (AtUSP) that has high activity with UDP-glucuronic acid (UDP-GlcA). AtUSP is predicted to be a cytosolic protein that belongs to a pyrophosphorylase family distantly related to the UDP-glucose and UDP-N-acetylglucosamine pyrophosphorylase families. The recombinant enzyme expressed in E. coli had high activity with GlcA-1-P, glucose-1-P, and galactose-1-P but very low activity with N-acetylglucosamine-1-P, fucose-1-P, mannose-1-P, inositol-1-P, or glucose-6-P. AtUSP had apparent Kms for GlcA-1-P, glucose-1-P, and UTP of 0.13 mM, 0.42 mM, and 0.14 mM, respectively. In the reverse direction the apparent Kms were 0.56 mM for UDP-GlcA, 0.72 mM for UDP-glucose, and 0.15 mM for pyrophosphate. Evaluation of AtUSP expression in plants by semiquantitative RT-PCR and enzyme activity assays indicated that the transcript and enzyme are widely expressed. This suggests that AtUSP is present in actively growing tissues where it may provide UDP-GlcA for cell wall synthesis.