Regulation of Cyanogenesis in Cassava

White, Wanda L.B.; McMahon, Jennifer M.; Sayre, Richard T.

doi:10.17660/actahortic.1994.375.4

Cited by 59 publications

(51 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…In sorghum (Sorghum bicolor) leaves, the cyanogenic glycoside dhurrin is located in vacuoles of leaf epidermal cells, whereas the ␤-glucosidase and HNL are localized in the cytoplasm and plastids of mesophyll cells (Poulton, 1990;Wajant et al, 1994). In cassava leaves linamarin has been localized to the vacuoles, whereas linamarase is localized to cell walls and laticifers (Mkpong et al, 1990;Pancoro and Hughes, 1992;Hughes et al, 1994;McMahon et al, 1995) Recently, we demonstrated that both linamarase and HNL were enriched (8-fold relative to whole leaves) in cassava leaf apoplast extracts (White et al, 1994;White and Sayre, 1995). These results suggested that HNL may be present in the cell walls.…”

Section: Discussionmentioning

confidence: 70%

“…Previously, we have demonstrated that leaf apoplast extracts were enriched (8-fold) in HNL activity relative to whole-leaf extracts, suggesting that HNL was probably localized in the cell walls (White et al, 1994;White and Sayre, 1995). To test this hypothesis, we carried out in situ immunolocalization of HNL in cassava leaves.…”

Section: Tissue-specific Localization Of Hnl In Cassavamentioning

confidence: 95%

“…Hydrolysis of linamarin yields an unstable hydroxynitrile intermediate, acetone cyanohydrin, plus Glc. Acetone cyanohydrin spontaneously decomposes to acetone and HCN at pH Ͼ5.0 or temperatures Ͼ35°C and can be broken down enzymatically by HNL (Cutler and Conn, 1981;Yemm and Poulton, 1986;Wajant and Mundry, 1993;Wajant et al, 1994;White et al, 1994;White and Sayre, 1995;Zheng and Poulton, 1995;Hasslacher et al, 1996;Wajant and Pfizenmaier, 1996).…”

mentioning

confidence: 99%

See 2 more Smart Citations

Cyanogenesis in Cassava1

White¹,

Arias-Garzon²,

McMahon³

et al. 1998

Plant Physiology

114

View full text Add to dashboard Cite

In the cyanogenic crop cassava (Manihot esculenta, Crantz), the final step in cyanide production is the conversion of acetone cyanohydrin, the deglycosylation product of linamarin, to cyanide plus acetone. This process occurs spontaneously at pH greater than 5.0 or enzymatically and is catalyzed by hydroxynitrile lyase (HNL). Recently, it has been demonstrated that acetone cyanohydrin is present in poorly processed cassava root food products. Since it has generally been assumed that HNL is present in all cassava tissues, we reinvestigated the enzymatic properties and tissue-specific distribution of HNL in cassava. We report the development of a rapid two-step purification protocol for cassava HNL, which yields an enzyme that is catalytically more efficient than previously reported (Hughes, J., Carvalho, F., and Hughes, M.[1994] Arch Biochem Biophys 311: 496-502). Analyses of the distribution of HNL activity and protein indicate that the accumulation of acetone cyanohydrin in roots is due to the absence of HNL, not to inhibition of the enzyme. Furthermore, the absence of HNL in roots and stems is associated with very low steady-state HNL transcript levels. It is proposed that the lack of HNL in cassava roots accounts for the high acetone cyanohydrin levels in poorly processed cassava food products.

show abstract

Section: Discussionmentioning

confidence: 70%

Section: Tissue-specific Localization Of Hnl In Cassavamentioning

confidence: 95%

mentioning

confidence: 99%

See 1 more Smart Citation

Cyanogenesis in Cassava1

White¹,

Arias-Garzon²,

McMahon³

et al. 1998

Plant Physiology

114

View full text Add to dashboard Cite

show abstract

“…During cyanogenesis, Glc is cleaved from linamarin by the enzyme linamarase. The resulting acetone cyanohydrin is unstable and degrades spontaneously at pH levels higher than 5.0 or temperatures greater than 35°C, or enzymatically by hydroxynitrile lyase in leaves, releasing hydrogen cyanide and acetone (Cutler and Conn, 1981;Hughes et al, 1994;White et al, 1994White et al, , 1998White and Sayre, 1995). However, cyanide release generally does not happen in intact cells because linamarin is localized in the vacuole, while the deglycosylase, linamarase, is localized in the cell wall and in laticifers (Mkpong et al, 1990;Hughes et al, 1994;McMahon et al, 1995).…”

Section: Discussionmentioning

confidence: 99%

Extending Cassava Root Shelf Life via Reduction of Reactive Oxygen Species Production

Zidenga

Leyva-Guerrero²,

Moon³

et al. 2012

Plant Physiology

138

168

View full text Add to dashboard Cite

One of the major constraints facing the large-scale production of cassava (Manihot esculenta) roots is the rapid postharvest physiological deterioration (PPD) that occurs within 72 h following harvest. One of the earliest recognized biochemical events during the initiation of PPD is a rapid burst of reactive oxygen species (ROS) accumulation. We have investigated the source of this oxidative burst to identify possible strategies to limit its extent and to extend cassava root shelf life. We provide evidence for a causal link between cyanogenesis and the onset of the oxidative burst that triggers PPD. By measuring ROS accumulation in transgenic low-cyanogen plants with and without cyanide complementation, we show that PPD is cyanide dependent, presumably resulting from a cyanide-dependent inhibition of respiration. To reduce cyanide-dependent ROS production in cassava root mitochondria, we generated transgenic plants expressing a codon-optimized Arabidopsis (Arabidopsis thaliana) mitochondrial alternative oxidase gene (AOX1A). Unlike cytochrome c oxidase, AOX is cyanide insensitive. Transgenic plants overexpressing AOX exhibited over a 10-fold reduction in ROS accumulation compared with wild-type plants. The reduction in ROS accumulation was associated with a delayed onset of PPD by 14 to 21 d after harvest of greenhouse-grown plants. The delay in PPD in transgenic plants was also observed under field conditions, but with a root biomass yield loss in the highest AOX-expressing lines. These data reveal a mechanism for PPD in cassava based on cyanideinduced oxidative stress as well as PPD control strategies involving inhibition of ROS production or its sequestration.

show abstract

“…Linamarin exist in all cassava tissues (Balagopalan et al 1988) and is synthesised from the amino acid valine. Cyanogenesis is initiated in physically damaged cassava tissues since cyanogenic and cyanogens enzymes are differently compartmentalised in the cell (White et al 1994). Therefore, after tissue maceration, linamarin is released from vacuoles, which then broke down to acetone cyanohydrin and glucose by linamarase (White et al 1994).…”

Section: Cyanide Levels In the Cassava Samplesmentioning

confidence: 99%

Human health risk assessment of cyanide levels in water and tuber crops from Kenyasi, a mining community in the Brong Ahafo Region of Ghana

et al. 2017

View full text Add to dashboard Cite

Background: Cyanide is among the most harmful substances on Earth and it is harmful to humans and most aquatic life even at low concentrations. Free, total cyanide levels and other physicochemical parameters were determined in fish, cassava, cocoyam, dam and borehole water samples collected from Kenyasi, Ghana. A total of sixteen (16) that the variation in free cyanide levels was significant (p < 0.05) in the fish, cassava, cocoyam, dam and borehole water samples. Moreover, the hazard index results via ingestion and dermal contact with children are >1, including fish ingestion by an adult. This signifies adverse non-carcinogenic risk. The persistent intake of cassava and cocoyam can probably induce adverse health effects. Conclusions: From the results, it can be concluded that fish, cassava and water samples at Dam 4, Dam 7 and BH1 were not safe for consumption since they recorded values higher than the set limits. Therefore, people are advised not to feed on the cassava product, fish and consume water samples located close to Dam 4, Dam 7 and BH1.

show abstract

Regulation of Cyanogenesis in Cassava

Cited by 59 publications

References 0 publications

Cyanogenesis in Cassava1

Cyanogenesis in Cassava1

Extending Cassava Root Shelf Life via Reduction of Reactive Oxygen Species Production

Human health risk assessment of cyanide levels in water and tuber crops from Kenyasi, a mining community in the Brong Ahafo Region of Ghana

Contact Info

Product

Resources

About