Cyclitols

Loewus, Frank A.; Dickinson, David B.

doi:10.1007/978-3-642-68275-9_6

Cited by 19 publications

(21 citation statements)

References 137 publications

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“…Myo-inositol is biosynthesized by myo-inositol-1-phosphate synthase (INPS, BE644574). As reported by Nelson and others 1998, INPS regulates the myo-inositol biosynthesis pathway (Nelson and others 1998), which is a specific pathway in salt tolerance in the common ice plant (Loewus and Dickinson 1982;Vernon and Bohnert 1992), and its expression can be feedbackinhibited by myo-inositol. In higher plants, betaine is synthesized by oxidation of choline: choline ?…”

Section: Discussionmentioning

confidence: 84%

Effects of Salinity on Metabolic Profiles, Gene Expressions, and Antioxidant Enzymes in Halophyte Suaeda salsa

Liu

You

et al. 2011

J Plant Growth Regul

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Halophyte Suaeda salsa is native to the saline soil in the Yellow River Delta. Soil salinity can reduce plant productivity and therefore is the most important factor for the degradation of wetlands in the Yellow River Delta. In this work we characterized the salinity-induced effects in S. salsa in terms of metabolic profiling, antioxidant enzyme activities, and gene expression quantification. Our results showed that salinity inhibited plant growth of S. salsa and upregulated gene expression levels of myo-inositol-1-phosphate synthase (INPS), choline monooxygenase (CMO), betaine aldehyde dehydrogenase (BADH), and catalase (CAT), and elevated the activities of superoxide dismutase (SOD), peroxidase (POD), CAT, and glutathione peroxidase (GPx). The significant metabolic responses included the depleted amino acids malate, fumarate, choline, phosphocholine, and elevated betaine and allantoin in the aboveground part of S. salsa seedlings as well as depleted glucose and fructose and elevated proline, citrate, and sucrose in root tissues. Based on these significant biological markers, salinity treatments induced clear osmotic stress (for example, INPS, CMO, BADH, betaine, proline) and oxidative stress (for example, SOD, POD, CAT, GPx activities), disturbed protein biosynthesis/degradation (amino acids and total protein) and energy metabolism (for example, glucose, sucrose, citrate) in S. salsa.

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Section: Discussionmentioning

confidence: 84%

Effects of Salinity on Metabolic Profiles, Gene Expressions, and Antioxidant Enzymes in Halophyte Suaeda salsa

Liu

You

et al. 2011

J Plant Growth Regul

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“…Changes of the hydroxyl configuration at the second (scyllo-) or sixth (epi-) carbon (17) of inositol can result in a >90% reduction in total activity. Altering the hydroxyl configuration at the fourth carbon (UDP-Glc) or substituting an acid group at the sixth position (UDP-GalUA) of the UDP-Gal drastically reduced the activity ofthe purified zucchini GS (Table II).…”

Section: Effects Of Various Metabolitesmentioning

confidence: 99%

Purification and Characterization of Galactinol Synthase from Mature Zucchini Squash Leaves

Smith¹,

Kuo²,

Crawford³

1991

Plant Physiol.

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Galactinol synthase catalyzes the first committed step in the biosynthesis of raffinose sugars. Previous attempts to purify the enzyme have proven difficult and have resulted in low quantities of unpurified enzyme. Galactinol synthase was purified 752-fold from mature zucchini (Cucurbita pepo L. cv Burpee Hybrid) leaves using sequential liquid chromatography on DE 52, Octyl-Sepharose CL-4B, and Sephacryl S-200. This isolation scheme resulted in an 18.6% recovery of the initial activity. The purified enzyme had a specific activity of 23.3 micromoles per minute per milligram protein, a pH optimum of 7.5, and the activity was enhanced by dithiothreitol and MnCI2. The enzyme was only half as active with MgCI2 as with MnCI2. Na+, K+, and Ca2+ cations had little effect on the enzyme activity, while Co2+, Zn2+, Cu2 , and Fe3+ cations were strongly inhibitory at 10 millimolar concentrations. Purified galactinol synthase bound specifically to the substrates myoinositol and UDP-galactose (Km = 6.5 and 1.8 millimolar, respectively), while exhibiting little affinity for an alternative glycosyl donor (UDP-glucose) or inositol epimers (epi-and scyllo-). Ten millimolar concentrations of UMP, UDP, UTP, AMP, ADP, ATP, NAD+, NADH, NADP+, UDP-xylose, and UDP-mannose, or 20 millimolar sucrose, talose, galactose, glucose, xylose, and melibiose exhibited various degrees of inhibitory effects. Twenty millimolar stachyose, raffinose, fructose, and mannose, and 10 millimolar UDP-glucuronic acid and UDP-galacturonic acid had little or no effect on the enzyme activity. The purified galactinal synthase is a monomer of Mr 42,000 with an isoelectric point of 4.1.The raffinose family ofoligosaccharides is the second largest group of sugars present in plant tissues (5). In many species, particularly the Cucurbita, these oligosaccharides (raffinose, stachyose, and verbascose) serve as transport sugars (19). Raffinose saccharide biosynthesis is initiated by the transfer of a galactosyl unit from galactinol (O-a-D-galactopyranosyl myo-inositol) to Suc to produce raffinose; this reaction is further iterated to yield stachyose and verbascose (15). Galactinol is synthesized from UDP-Gal and myo-inositol by UDP-D-a-galactose:inositol galactosyltransferase or GS2 (15) as shown below:UDP-Gal + myo-inositol *-* galactinol + UDP 'Supported in part by a grant from the American Soybean Association to T. M. K.

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“…The analysis of the role of UDP-GlcDH is further complicated by the existence of a second biosynthetic route for UDP-GlcUA called the inositol oxidation pathway (Loewus and Dickinson, 1982) (Fig. 1, right side).…”

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confidence: 99%

Cloning of an Enzyme That Synthesizes a Key Nucleotide-Sugar Precursor of Hemicellulose Biosynthesis from Soybean:UDP-Glucose Dehydrogenase

1996

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Hemicellulose is a major component of primary plant cell walls. Many of the glycosyl residues found in hemicellulose are derived from the sugar precursor UDP-glucuronic acid, which can be converted into UDP-arabinose, UDP-apiose, UDP-galacturonic acid, and UDP-xylose. The enzyme controlling the biosynthesis of UDPglucuronic acid, UDP-glucose dehydrogenase (EC 1.1.1.22), was cloned from soybean (Clycine max [L.] Merr.) by an antibody screening procedure. This enzyme is surprisingly homologous to the bovine sequence, which is the only other eukaryotic UDP-glucose dehydrogenase sequence known. The characteristic motifs of the enzyme, the catalytic center, a NAD-binding site, and two proline residues for main chain bends, are conserved within the prokaryotic and eukaryotic sequences. The soybean full-length cDNA clone encodes a protein of 480 amino acids with a predicted size of 52.9 kD. The enzyme is highly expressed in young roots, but lower expression levels were observed in expanding tissues of the epicotyl and in young leaves. The expression pattern of the enzyme in different developmental stages strengthens the argument that UDPglucose dehydrogenase is a key regulator for the availability of hemicelluose precursors.

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Cyclitols

Cited by 19 publications

References 137 publications

Effects of Salinity on Metabolic Profiles, Gene Expressions, and Antioxidant Enzymes in Halophyte Suaeda salsa

Effects of Salinity on Metabolic Profiles, Gene Expressions, and Antioxidant Enzymes in Halophyte Suaeda salsa

Purification and Characterization of Galactinol Synthase from Mature Zucchini Squash Leaves

Cloning of an Enzyme That Synthesizes a Key Nucleotide-Sugar Precursor of Hemicellulose Biosynthesis from Soybean:UDP-Glucose Dehydrogenase

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