Subcellular Localization of a UDP-Glucose:Aldehyde Cyanohydrin β-Glucosyl Transferase in Epidermal Plastids of <i>Sorghum</i> Leaf Blades

Wurtele, Eve Syrkin; Thayer, Susan S.; Conn, Eric E.

doi:10.1104/pp.70.6.1732

Cited by 20 publications

(10 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Dhurrin and the majority of the UDP-glucose:aldehyde cyanohydrin (l-glucosyl transferase activity are located in the epidermal protoplasts (13,22) while the ,3-glucosidase specific for dhurrin hydrolysis is in the mesophyll protoplasts (13,21). Upon leaf injury, dhurrin is hydrolyzed and HCN is released.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Tissue Distribution of β-Cyanoalanine Synthase in Leaves

Wurtele

Nikolau²,

Conn³

1984

Plant Physiol.

Self Cite

View full text Add to dashboard Cite

ABSTRACI,j-Cyanoalanine synthase, which catalyzes the reaction between cysteine and HCN to form 6-cyanoalanine and H2S, was assayed in leaf tissues from cyanogenic (Sorghum bicolor x Sorgkum sudawease [sorghum]) and noncyanogenic (Pisum sativum Ipeal Zea mays [maizel, and Allium porrum Pleek]) plants. The activity in whole kaf extracts ranged from 33 nanomoles per gram fresh weight per minute in leeks, to 1940 nanomoles per gram fresh weight per minute in sorghum. The specific activities of 6-cyanoalanine synthase in epidermal protoplasts from maize and sorghum and in epidermal tissues from peas were in each case greater than the corresponding values for mesophyll protoplasts or tissues, or for strands of bundle sheath cells.The tissue distributions for this enzyme were determined for pea, leek, and sorghum: the mesophyll protoplasts and tissues in these three plants contained 65% to 78% of the enzyme, while epidermal protoplasts and tissues contained 10% to 35% of the total leaf activity. In sorghum, the bundle sheath strands contained 13% of the leaf activity. The presence of,-cyanoalanine synthase in all tissues and species studied suggests a fundamental role for this enzyme in plant metabolism.13-Cyanoalanine synthase (EC 4.4.1.9), which catalyzes the reaction between cysteine and HCN to form (l-cyanoalanine and H2S (4), is widely distributed in higher plants (4,11,16). Although the enzyme has been purified and its kinetic properties examined (1, 12), its role(s) in plant metabolism have not yet been defined (see 8 for review). ,3-Cyanoalanine hydratase (EC 4.2.1.65) catalyzes the hydration of (B-cyanoalanine to form asparagine (6). The sequential action of these two enzymes constitutes an effective mechanism for detoxifying HCN while conserving the nitrogen atom in the form of amide nitrogen. Such a role for these enzymes in cyanide detoxification is supported by studies (4,5,17) showing that gaseous, '4C-labeled HCN is incorporated in high yields into asparagine when administered to either cyanogenic or noncyanogenic species. In addition, experiments demonstrating the detoxification of HCN produced in vivo during the metabolic turnover of cyanogenic glycosides in Lotus sp., Nandina domestica, and Manihot utilissima have been described (2, 3,17). Asparagine synthesis in Asparagus officinalis has also been attributed to this two-step metabolic sequence (9), but the source of the HCN required as a substrate was not identified.Recent studies by Peiser et aL (19)

show abstract

mentioning

confidence: 99%

“…Activity in the tissue indicated which could be isolated from I g fresh weight of leaf. ously described (22). Sorghum seedlings were harvested at 5.5 d after planting and were 3 to 7 cm tall with two expanded leaves.…”

mentioning

confidence: 99%

Tissue Distribution of β-Cyanoalanine Synthase in Leaves

Wurtele

Nikolau²,

Conn³

1984

Plant Physiol.

Self Cite

View full text Add to dashboard Cite

show abstract

“…The biosynthesis of cuticular waxes has also been demonstrated to be in the epidermis of leaves (19). UDP-glucose aldehyde cyanohydrin figlucosyl transferase, the final enzyme of dhurrin biosynthesis, is localized predominantly in the epidermal cells of sorghum (17,30).…”

Section: Discussionmentioning

confidence: 99%

“…Seeds of maize (Zea mays, var Golden Hybrid Blend), pea (Pisum sativum, Argentum mutant) (14), and a sorghum ([Sorghum bicolor (L.) Moench] x sudan grass [S. sudanense (Piper) StapfJ hybrid [cv WAC Forage 99]) were soaked, planted, and allowed to germinate under conditions previously described (30).…”

Section: Methodsmentioning

confidence: 99%

Enzymes of Glucose Oxidation in Leaf Tissues

Wurtele

Nikolau²

1986

Plant Physiol.

Self Cite

View full text Add to dashboard Cite

ABSTRACIThe distribution of the glycolytic enzymes, phosphofructokinase, aldolase, triosephosphate isomerase, phosphoglycerate kinase, pyruvate kinase, and the oxidative pentose phosphate pathway enzymes, glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase, was determined in the leaf tissues of two C3-plants, pea and leek, and two C4-plants, maize and sorghum. All enzymes examined were found in epidermal tissue. In pea, maize, and sorghum leaves, the specific activities of these enzymes were usually higher in the nonphotosynthetic epidermal tissue than in the photosynthetic tissues of the leaves. In leek leaves, which were etiolated, specific activities were similar in both epidermal and mesophyll tissue. The distribution of the rate limiting enzymes of glycolysis and the oxidative pentose phosphate pathways probably reflects the capacity of each tissue to generate NADH, NADPH, and ATP from the oxidation of glucose. This capacity appears to be greater in leaf tissues unable to generate reducing equivalents and ATP by photosynthesis, that is, in epidermal tissues and etiolated mesophyll tissue.Microscopic examination of leaves readily demonstrates the diversity of cell types in this organ (9,16 cells (14, 17-19, 23, 28, 30).Glycolysis and the oxidative pentose phosphate pathway are the major routes of glucose oxidation in plants, providing ATP, NADH, and NADPH to nonphotosynthetic cells in the light,

show abstract

“…Cyanogenic glucosides are found in plant species of more than 130 families and have important functions in plant defense against herbivores and pathogens [1][2][3]. Unfortunately as constituents in plant-based food cyanogenic glucosides are extremely undesirable because they can be converted to hydrocyanic acid, a highly poisonous compound, when encounter glycosidase or under low pH in the digestive tracks of animals [4][5][6][7][8][9][10]. Flax (Linum unsitatissimum) is one of the major economic crops known to possess high level of cyanogenic glucosides, linamarin and lotaustralin [11].…”

Section: Introductionmentioning

confidence: 99%

Molecular identification and functional characterization of a cyanogenic glucosyltransferase from flax (Linum unsitatissimum)

Kazachkov

Shen

et al. 2020

PLoS ONE

View full text Add to dashboard Cite

Flax seed has become consumers' choice for not only polyunsaturated alpha-linolenic fatty acid but also nutraceuticals such as lignans and soluble fiber. There is, however, a major drawback of flax as a source of functional food since the seeds contain significant level of cyanogenic glucosides. The final step of cyanogenic glucoside biosynthesis is mediated by UDP-glucose dependent glucosyltransferase. To date, no flax cyanogenic glucosyl transferase genes have been reported with verified biochemical functionality. Here we present a study on the identification and enzymatic characterization of a first flax cyanogenic glucosyltransferase, LuCGT1. We show that LuCGT1 was highly active towards both aliphatic and aromatic substrates. The LuCGT1 gene is expressed in leaf tissues as well as in developing seeds, and its expression level was drastically reduced in flax mutant lines low in cyanogenic glucosides. Identification of LuCGT1 provides a molecular handle for developing gene specific markers for targeted breeding of low cyanogenic glucosides in flax.

show abstract

Subcellular Localization of a UDP-Glucose:Aldehyde Cyanohydrin β-Glucosyl Transferase in Epidermal Plastids of Sorghum Leaf Blades

Cited by 20 publications

References 16 publications

Tissue Distribution of β-Cyanoalanine Synthase in Leaves

Tissue Distribution of β-Cyanoalanine Synthase in Leaves

Enzymes of Glucose Oxidation in Leaf Tissues

Molecular identification and functional characterization of a cyanogenic glucosyltransferase from flax (Linum unsitatissimum)

Contact Info

Product

Resources

About