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Query: UNIPROT:P06889 (Mol)
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UDP-glucose: protein transglucosylase (UPTG, EC 2.4.1.112) catalyzes the first step of protein-bound alpha-glucan synthesis in potato tuber and developing maize endosperm. The presence of a non-dialyzable, heat labile protein responsible for low levels of UPTG activity in developing maize endosperm was investigated. UPTG activity in 5-day old maize seedlings and potato tuber solubilized preparations was also reduced by the endosperm preparation. FPLC-Mono Q column chromatography of developing maize endosperm was effective in separating the inhibitor protein (IP) from UPTG. After gel filtration on Superose 12, IP yielded a major polypeptide of about 80 kDa on SDS-PAGE. IP was purified by gel filtration on Superose 12 and preparative SDS-PAGE, and specific antibodies were prepared. Polyclonal antibodies reacted specifically with an 80 kDa polypeptide of developing maize endosperm on Western blot. They also recognized a similar band in 5-day old maize seedlings, but not in potato tubers. The identification of a factor that regulates the level of UPTG activity in developing maize endosperm may help to elucidate the functional role of the enzyme in the initiation of starch synthesis during seed development.
Cell Mol Biol (Noisy-le-grand) 1996 Jul
PMID:Inhibition of UDP-glucose: protein transglucosylase by a maize endosperm protein factor. 883 94

Many plant autocatalytic glycosyltransferases are implicated in plant polysaccharide biosynthesis. Cloning of cDNAs encoding potato (Solanum tuberosum L.) UDP-Glc:protein transglucosylase (UPTG, EC 2.4.1.112) and expression of the cDNA clone E11 in Escherichia coli have been previously reported. Here, we studied the functional expression of a second cDNA of the enzyme (E2 clone). Northern blots analysis, with specific cDNA probes for the two UPTG isoforms, showed a differential expression pattern of mRNA levels in different potato tissues. Moreover, both UPTG recombinant enzymes showed different kinetic parameters. The recombinant protein encoded by E2 clone has an apparent Imax for UDP-Xyl and UDP-Gal, significantly higher than for UDP-Glc. The Km values for UDP-Glc were 0.45-0.71 microM and the values for UDP-Xyl and UDP-Gal were slightly higher than that of the UDP-Glc (1.2-2.71 microM) for both UPTG recombinant enzymes. The present study revealed further evidence for the proposed role of UPTG in the synthesis of cell wall polysaccharide. It was found a correlation between UPTG transcript levels and the growing state of the tissues in which there was an active synthesis of cell wall components. Southern blot analysis indicates that at least three genes encoding UPTG are present in potato genome. Phylogenetic analysis of both UPTG recombinant proteins showed that they are members of the RGP subfamilies from dicots.
Plant Mol Biol 2003 Jul
PMID:Characterization of UDP-glucose:protein transglucosylase genes from potato. 1367 61