Aldo (and Keto) Hexoses and Uronic Acids

Feingold, David S.

doi:10.1007/978-3-642-68275-9_1

Cited by 34 publications

(46 citation statements)

References 370 publications

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“…To date, only a small number of RhaTs have been studied, and those were involved in flavonoid rhamnosylation. The characterized RhaTs utilize UDP-b-L-rhamnose (UDP-b-L-Rha) as the donor substrate (Kamsteeg et al, 1978;Feingold, 1982;Bar-Peled et al, 1991), although in mung bean (Vigna radiata), both dTDP-b-L-rhamnose (dTDP-b-L-Rha) and UDP-b-L-Rha were reported to act as sugar donors for the rhamnosylation of flavonoids (Barber and Neufeld, 1961).We are studying the enzymes involved in the synthesis of the nucleotide-rhamnose as part of our effort to understand the synthesis of pectic polysaccharides. To date, the rhamnosylation of plant polysaccharides and glycoproteins has not been studied.…”

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“…1). Since at least some plants generate dTDP-a-D-Glc (Milner and Avigad, 1965;Delmer and Albersheim, 1970) in addition to UDP-a-D-Glc, formation of dTDP-b-L-Rha from dTDP-a-D-Glc was reported as well (for review, see Feingold, 1982). Less is known about the subsequent reactions in the pathway, and it was suggested that the 3,5-epimerization and 4-reduction is mediated by a single enzyme (Kamsteeg et al, 1978).…”

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A Bifunctional 3,5-Epimerase/4-Keto Reductase for Nucleotide-Rhamnose Synthesis in Arabidopsis

et al. 2004

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L-Rhamnose is a component of plant cell wall pectic polysaccharides, diverse secondary metabolites, and some glycoproteins. The biosynthesis of the activated nucleotide-sugar form(s) of rhamnose utilized by the various rhamnosyltransferases is still elusive, and no plant enzymes involved in their synthesis have been purified. In contrast, two genes (rmlC and rmlD) have been identified in bacteria and shown to encode a 3,5-epimerase and a 4-keto reductase that together convert dTDP-4-keto-6-deoxy-Glc to dTDP-b-L-rhamnose. We have identified an Arabidopsis cDNA that contains domains that share similarity to both reductase and epimerase. The Arabidopsis gene encodes a protein with a predicated molecular mass of approximately 33.5 kD that is transcribed in all tissue examined. The Arabidopsis protein expressed in, and purified from, Escherichia coli converts dTDP-4-keto-6-deoxy-Glc to dTDP-b-L-rhamnose in the presence of NADPH. These results suggest that a single plant enzyme has both the 3,5-epimerase and 4-keto reductase activities. The enzyme has maximum activity between pH 5.5 and 7.5 at 308C. The apparent K m for NADPH is 90 mM and 16.9 mM for dTDP-4-keto-6-deoxy-Glc. The Arabidopsis enzyme can also form UDP-b-L-rhamnose. To our knowledge, this is the first example of a bifunctional plant enzyme involved in sugar nucleotide synthesis where a single polypeptide exhibits the same activities as two separate prokaryotic enzymes.L-Rhamnose is a component of the plant cell wall pectic polysaccharides rhamnogalacturonan I (RG-I) and rhamnogalacturonan II (RG-II; Ridley et al., 2001) and is also present in diverse secondary metabolites including anthocyanins, flavonoids, and triterpenoids (Das et al., 1987;Bar-Peled et al., 1991;van Setten et al., 1995;Shinozaki et al., 1996;Markham et al., 2000), in certain types of plant glycoproteins (Haruko and Haruko, 1999), and in arabinogalactan proteins (Pellerin et al., 1995). The specific enzymes that attach rhamnose to each molecule are known as rhamnosyltransferases (RhaTs). To date, only a small number of RhaTs have been studied, and those were involved in flavonoid rhamnosylation. The characterized RhaTs utilize UDP-b-L-rhamnose (UDP-b-L-Rha) as the donor substrate (Kamsteeg et al., 1978;Feingold, 1982;Bar-Peled et al., 1991), although in mung bean (Vigna radiata), both dTDP-b-L-rhamnose (dTDP-b-L-Rha) and UDP-b-L-Rha were reported to act as sugar donors for the rhamnosylation of flavonoids (Barber and Neufeld, 1961).We are studying the enzymes involved in the synthesis of the nucleotide-rhamnose as part of our effort to understand the synthesis of pectic polysaccharides. To date, the rhamnosylation of plant polysaccharides and glycoproteins has not been studied. Thus, the identity of the activated form(s) of rhamnose needed for the synthesis of these macromolecules is not known with certainty. The enzymes required for the synthesis of the activated form(s) of rhamnose in plants have also not been purified.In contrast, much more is known about the synthesis of rhamnose in...

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A Bifunctional 3,5-Epimerase/4-Keto Reductase for Nucleotide-Rhamnose Synthesis in Arabidopsis

et al. 2004

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“…For many reasons, recycling of sugars has been difficult to assess. Several studies have employed sugars such as L-arabinose and D-galactose, because salvage pathways beginning with C-1 kinases result in formation ofa few specific nucleotide-sugars (20,34), hence specific polymers (1 1, 36). However, assessing the recycling of sugars is a problem because C-I kinases salvage the very sugars that recycle, and label never completely leaves these sugars.…”

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“…We have used arabinose as a radioactive tracer because only polymers containing arabinose and xylose become radioactive. Both arabinose and xylose are formed by pathways of nucleotide-sugar interconversion whereby UDPGlc is oxidized to UDP-GlcA and subsequently decarboxylated to UDP-Xyl (20). A C-4 epimerase interconverts UDPXyl to UDP-Ara (20).…”

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Tracing Cell Wall Biogenesis in Intact Cells and Plants

Gibeaut¹,

Carpita²

1991

Plant Physiol.

197

104

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binose into soluble and cell wall polymers. Radioactivity from arabinose accumulated selectively in polymers containing arabinose or xylose because a salvage pathway and C-4 epimerase yield both nucleotide-pentoses. On the other hand, radioactivity from glucose was found in all sugars and polymers. Pulse-chase experiments with proso millet cells in liquid culture demonstrated turnover of buffer soluble polymers within minutes and accumulation of radioactive polymers in the cell wall. In leaves of maize seedlings, radioactive polymers accumulated quickly and peaked 30 hours after the pulse then decreased slowly for the remaining time course. During further growth of the seedlings, radioactive polymers became more tenaciously bound in the cell wall. Sugars were constantly recycled from tumover of polysaccharides of the cell wall. Arabinose, hydrolyzed from glucuronoarabinoxylans, and glucose, hydrolyzed from mixed-linkage (1-.3,1-+4)#-D-glUcans, constituted most of the sugar participating in turnover. Arabinogalactans were a large portion of the buffer soluble (cytoplasmic) polymers of both proso millet cells and maize seedlings, and these polymers also exhibited turnover. Our results indicate that the primary cell wall is not simply a sink for various polysaccharide components, but rather a dynamic compartment exhibiting long-term reorganization by turnover and alteration of specific polymers during development.A concept of plant growth which addresses development as a continuous process must integrate both cell wall "loosening" and cell wall synthesis in the mechanics of cell expansion. Hormone-induced increases in wall extensibility are unequivocal and considered by many as the rate limiting factor in expansion (for review, see ref. 39), but cell wall synthesis is indeed necessary for continuous plant growth (3,19,29 an early burst of growth as a result of a rapid induction of wall loosening and a later steady rate of growth. The second phase of sustained growth ensued after the hormone induced tissues reorganized their entire growth machinery. The continuous growth of intact plants is more similar to this second phase. Most of the evidence indicates that auxin-induced increases in cell wall synthesis are important for this sustained growth (3,19,29). However, other important biochemical processes not well characterized heretofore are the changing quantity and type of polysaccharide and their selective alteration in muro.Polysaccharide synthesis and metabolism can be followed by the flow and accumulation of radioactivity from sugar substrates into cellular compartments and specific polysaccharides. Although incorporation and distribution of sugars can be monitored conveniently in excised tissues, excision severely limits the time course of study and interrupts normal carbon assimilation. Alternatively, cells in liquid culture offer a convenient model to study synthesis and distribution of polymers without excision or interruption of carbon supply. However, proso millet cells (Panicum miliaceum L. cv Abarr), lik...

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“…Free MI is a common constituent of plants, probably ubiquitous, and it is utilized in numerous metabolic processes of which the MI oxidation pathway has emerged as highly significant due to its biosynthetic role as a source of UDP-D-glucuronate (9,13,14). Oxidation of MI to D-glucuronate is probably the first committed step in UDP-D-glucuronate biosynthesis via MI but we choose to include MI biosynthesis in the overall process since MI-1-P synthase and MI-l-phosphatase directly link conversion ofglucose-6-P to UDP-D-glucuronate formation by processes operating independently of UDP-D-glucose dehydrogenase (EC 1.1.1.22) (17,26).…”

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myo-Inositol-1-Phosphatase from the Pollen of Lilium longiflorum Thunb.

Loewus¹,

Loewus²

1982

Plant Physiol.

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A Mg2"-dependent, alkaline phosphatase has been isolated from mature pollen of Lilium longiflorum Thunb., cv. Ace and partially purified. It hydrolyzes 1L-and lD-myo-inositol 1-phosphate, myo-inositol 2-phosphate, and f8-glycerophosphate at rates decreasing in the order named. The affinity of the enzyme for 1L-and 1n-myo-inositol 1-phosphate is approximately 10-fold greater than its affinity for myo-inositol 2-phosphate. Little or no activity is found with phytate, i-glucose 6- IL-MI-I-P,3 the product of lL-MI-l-P synthase (EC 5.5.1.4) is hydrolyzed to MI and Pi by MI-1-phosphatase (EC 3.1.3.5),4 a Mg2+-dependent enzyme that occurs in yeast (3), rat testis (8), rat mammary land (21), and bovine brain (12). The epimeric form ID-MI-1-P, also is hydrolyzed by MI-1-phosphatase at 80% to ' Supported by Grant GM-22427 2To whom inquiries and requests for reprints should be addressed.'Abbreviations: MI, myo-inositol; MI-1-P, myo-inositol-l-phosphate; MI-l-phosphatase, myo-inositol-l-phosphatase; glucose-6-P, D-glucose-6-phosphate.4In accord with a recent suggestion (12), the term MI-1-phosphatase is used rather than the more specific term 1 L-MI-1 -phosphatase. 5 Prior to 1968, systems of cyclitol nomenclature other than the one currently in use (1) were used to describe substituted inositols. Thus, the product of IL-MI-I-P synthase sometimes was designated D-MI-1-P or simply MI-3-P in contrast to the currently acceptable term, IL-MI-I-P.90o of the rate of the IL isomer. In a recent study of MI-1-phosphatase from chick erythrocytes (24) only the ID isomer was used as substrate but the properties of this enzyme indicate that it resembles those which hydrolyze both epimers of MI-1-P.Conversion of D-glucose to MI in plants involves enzymic steps similar to those encountered in animal tissues and fungi, and the epimeric form of the intermediate, MI-1-P, has been established as IL (MW Loewus, K Sasaki, AL Leavitt, L Munsell, WR Sherman, and FA Loewus, manuscript in preparation). Free MI is a common constituent of plants, probably ubiquitous, and it is utilized in numerous metabolic processes of which the MI oxidation pathway has emerged as highly significant due to its biosynthetic role as a source of UDP-D-glucuronate (9,13,14). Oxidation of MI to D-glucuronate is probably the first committed step in UDP-D-glucuronate biosynthesis via MI but we choose to include MI biosynthesis in the overall process since MI-1-P synthase and MI-l-phosphatase directly link conversion ofglucose-6-P to UDP-D-glucuronate formation by processes operating independently of UDP-D-glucose dehydrogenase (EC 1.1.1.22) (17, 26). In this regard, a Mg2"-dependent MI-l-phosphatase was detected in cellfree extract of Acer pseudoplatanus suspension cell culture (15). Subsequently, thi enzyme was found to be present in crude cellfree MI-I-P synthase preparations from other plant sources, notably that of lily pollen. This paper describes the isolation, purification, and properties of MI-l-phosphatase from lily pollen. A preliminary report appeared ...

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Aldo (and Keto) Hexoses and Uronic Acids

Cited by 34 publications

References 370 publications

A Bifunctional 3,5-Epimerase/4-Keto Reductase for Nucleotide-Rhamnose Synthesis in Arabidopsis

A Bifunctional 3,5-Epimerase/4-Keto Reductase for Nucleotide-Rhamnose Synthesis in Arabidopsis

Tracing Cell Wall Biogenesis in Intact Cells and Plants

myo-Inositol-1-Phosphatase from the Pollen of Lilium longiflorum Thunb.

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