UDPG Research Articles

Purification and Characterization of Sucrose Phosphate Synthase from Sweet Photato Tuberous Roots

Sucrose phosphate synthase (SPS) is one of the key enzymes in the sucrose biosynthesis pathway. SPS was purified 40 fold from crude extract of sweet potato tuberous roots by the methods of batch elution from DEAE-Sephacel, PEG precipitation, ω-aminohexyl Sepharose 4B affinity and Mono Q anion exchange chomatographies. The native- and SDS-PAGE analyses revealed SPS to have a native molecular mass of about 540kDa, and it may therefore be homotetramer composed of subunit with a mass of 130-140kDa. The isoelectric point of the purified enzyme as determined by IEF was 5.29. SPS from the sweet potato tuberous root, which differs from the SPS of photosynthetic tissues, was not allosterically regulated by G6P and Pi. The Km for F6P and UDPG was 5.3 and 31.3mM, respectively. The enzyme was activated by Mn (superscript 2+), Mg (superscript 2+), and Ca (superscript 2+), while being inhibited by Hg (superscript 2+). The nucleotides AMP, ADP, ATP, UMP, UDP, UTP, and TDP inhibited the enzyme about 30~50%. The enzyme was sensitive to sulfydryl reagents, but activity could be restored with DTT or β-ME. The enzyme was activated by glucose, glucosamine, maltose, and lactose, but was inhibited by δ-gluconolactone. SPS could also be inhibited by PCMBS and Cibacron blue F3G-A.

CYTOCHEMICAL STUDY OF ELECTRON MICROSCOPY ON FRUCTOSE 1,6-DIPHOSPHATASE AND URIDINE DIPHOS PHOGLUCOSE PYROPHOSPHORYLASE IN THE MESO PHYLL CELLS OF Stevia rebaudiana BERTONI

The subcellular localizations of fructose 1,6-diphosphatase (FDPase, EC 3.1.3.11) and uridine diphos- phoglucose pyrophosphorylase (UDPG PPlase, UTP:α-D-glucose-I-phosphate uridylytransferase, EC 2.7. 7.9) in the mesophyll cells of a new sweetener plant (Stevia rebaudiana Bertoni), both of which are critical in carbohydrate metabolism, were determined and the activities of both enzymes in the leaves of different ages were compared in this study. This experiment reveals: FDPase is a membrane-bound enzyme and is specifically localized on the thylakoid membranes of chloroplasts and the plasmic membranes. FDPase is only found on the thylakoid membranes of chloroplasts in the young mesophyll cells, while it is found on both the thylakoid membranes of chloroplasts and the plasmic membranes in the mature meso- phyll cells. UDPG PPlase is distributed in the cytoplasmic matrix freely, and is localized on Golgi flat- tened sacs and Colgi vesicles in a membrane-bound form. In this study, it is suggested that the chloroplasts, the cytoplasmic matrix and Golgi complex are important in the synthesis of stevioside.

Effect of fasting and phenobarbital on hepatic UDP-glucuronic acid formation in the rat.

Abstract Fasting causes a rise in the serum unconjugated bilirubin concentration in various animals and man. Prior administration of phenobarbital prevents this effect in patients with Gilbert's syndrome. The effect of fasting and phenobarbital on bilirubin glucuronidation was studied by measuring hepatic activity of bilirubin UDPG-T and UDPG-D and the hepatic content of UDPG and UDPGA in fed, fasted, phenobarbital-treated, and fasted and phenobarbital-treated rats. Fasting for 72 hr resulted in 44% and 59% decreases in the specific and absolute UDPG-D activities, respectively, and a 43% decrease in the UDPGA concentration (p 0.4). The specific activities of UDPG-T and UDPG-D were increased 61% (p 0.1), respectively, and the UDPGA concentration was increased 84% (p

On the non-identity of phosphorylase [formula omitted] kinase and UDPG:α-1,4-glucan α-4-glucosyltransferase

On the non-identity of phosphorylase [formula omitted] kinase and UDPG:α-1,4-glucan α-4-glucosyltransferase