Hydrolysis of the Cyanogenic Glycosides Amygdalin, Prunasin and Linamarin by Ruminal Microorganisms

Majak, W.; Cheng, K.-J.

doi:10.4141/cjas87-120

Cited by 21 publications

(9 citation statements)

References 4 publications

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“…Some researchers reported that heat processing of flaxseed did not change its HCN content 11. This could be due to the fact that the HCN formed after cyanogenic glycoside hydrolysis remain in flax products, or the deactivation of glycosidase in plant tissue could be replaced by the glycosidase formed by gut microflora 18–20. It is reasonable to state that effective flaxseed processing requires more than just cyanogenic glycoside hydrolysis or deactivation of glycosidase in tissue alone.…”

Section: Discussionmentioning

confidence: 99%

Effectiveness of different processing methods in reducing hydrogen cyanide content of flaxseed

2003

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A study was conducted to determine the effectiveness of reducing the hydrogen cyanide (HCN) content of flaxseed (FS) by processing. FS was processed by oven heating, single or repeated pelleting alone or in a mix with corn or other ingredients, autoclaving, and microwave roasting. The comparative effectiveness in reducing HCN in FS by these processes was monitored through HCN measurements by alkaline titration. The HCN content was 377 mg kg −1 in raw feed-grade FS and 139 mg kg −1 in a human food-grade FS. All processing methods tested significantly (p < 0.05) reduced the HCN content of FS. Autoclaving FS reduced its HCN content by 29.7%. Microwave roasting of FS reduced the HCN content by 83.3%. Because of the 5.7% water loss recorded after 4 min of FS roasting, this reduction could be related to more evaporation of the newly formed HCN. Pelleting FS once reduced HCN content by 13.3%, and three and six repeated pelleting processes reduced HCN content by 29.0% and 54.9% respectively. When FS was pelleted in a mix with 50% corn, the HCN reduction was even greater. After pelleting six times, HCN reduction reached 63.8%. However, the greatest reduction in HCN content was 73.8%, and was obtained when FS was mixed with several ingredients and pelleted twice. The HCN reduction could be the result of deactivation of the glycosidase, or the evaporation of HCN formed from cyanogenic glycosides. The HCN reduction increased as the number of pelletings and the temperature of the pelleted product increased. The greater and prolonged exposure to a higher temperature by several pelletings seems to promote a greater HCN reduction. The appropriate processing of FS is essential for the use of this oilseed in animal feeding.

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Section: Discussionmentioning

confidence: 99%

Effectiveness of different processing methods in reducing hydrogen cyanide content of flaxseed

2003

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“…Adverse growing conditions like drought can increase the level of cyanide present in plants (Pickrell et aI., 1991). Cyanide is detoxified in ruminants through the formation of thiocyanates produced either in the rumen or after absorption of cyanide from the gastrointestinal tract (Majak and Cheng, 1987;Onwuka et at., 1992;Salkowski and Penney, 1994). In the rumen, rates of cyanogenesis are pH-dependent, with high rates of cyanide production observed when ruminal pH exceeds 6.0 (Majak et at., 1990).…”

Section: Cyanogenic Gtycosidesmentioning

confidence: 99%

The Rumen Microbial Ecosystem

Hobson¹,

Stewart²

1997

347

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“…The high cyanogenic activity of mixed populations of ruminal bacteria (19,20) suggests that this is not an isolated case and that other enzymes with activity towards these cyanogenic compounds are present in the rumen. Preliminary qualitative studies indicate that CdxA is also capable of releasing free cyanide from both prunasin and amygdalin (data not shown).…”

mentioning

confidence: 99%

“…In the 1980s Majak and Cheng (19,20) demonstrated that many ruminal bacteria, including P. ruminicola, have the ability to release free cyanide from the glycosides amygdalin (laetrile), prunasin, and linamarin. ␤-Glucosidases play a key role in the initial step of hydrolyzing these compounds into glucose units and the cyanogenic aglycone (8,22).…”

mentioning

confidence: 99%

Cloning, sequencing, and characterization of a membrane-associated Prevotella ruminicola B(1)4 beta-glucosidase with cellodextrinase and cyanoglycosidase activities

Wulff-Strobel

Wilson

1995

J Bacteriol

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Prevotella ruminicola B 1 4 is a gram-negative, anaerobic gastrointestinal bacterium. A 2.4-kbp chromosomal fragment from P. ruminicola encoding an 87-kDa aryl-glucosidase (CdxA) with cellodextrinase activity was cloned into Escherichia coli DH5␣ and sequenced. CdxA activity was found predominantly in the membrane fraction of both P. ruminicola and E. coli, but P. ruminicola localized the protein extracellularly while E. coli did not. The hydrolase had the highest activity on cellodextrins (3.43 to 4.13 mol of glucose released min ؊1 mg of protein ؊1) and p-nitrophenyl-␤-D-glucoside (3.54 mol min ؊1 mg of protein ؊1). Significant activity (70% of p-nitrophenyl-␤-D-glucoside activity) was also detected on arbutin and prunasin. Less activity was obtained with cellobiose, amygdalin, or gentiobiose. CdxA attacks cellodextrins from the nonreducing end, releasing glucose units, and appears to be an exo-1,4-␤-glucosidase (EC 3.2.1.74) which also is able to attack ␤-1,6 linkages. Comparison of the deduced amino acid sequence with other glycosyl-hydrolases suggests that this enzyme belongs to family 3 (B. Henrissat, Biochem. J. 280:309-316, 1991). On the basis of this sequence alignment, the catalytic residues are believed to be Asp-275 and Glu-265. This is the first report of a cloned ruminal bacterial enzyme which can cleave cyanogenic plant compounds and which may therefore contribute to cyanide toxicity in ruminants.Ruminant animals such as cattle and sheep have evolved to utilize the extensive fermentative abilities of their reticuloruminal microflora. This symbiotic relationship gives the ruminant animal access to a variety of herbaceous foodstuffs such as cellulose and hemicellulose which are nutritionally unavailable to monogastric animals. In addition to cellobiose, cellodextrins are a major product of cellulose hydrolysis in the rumen. Ruminal bacteria that can utilize cellodextrins are common. Prevotella ruminicola B 1 4 possesses extracellular cellodextrinase activity (27) and can utilize water-soluble cellodextrins (up to seven glucose units in length) as carbon and energy sources. In this paper, we report the cloning, sequencing, and partial characterization of an 87-kDa membrane-associated exo-␤-glucosidase.Although normally beneficial, the expanded digestive repertoire of the ruminant animal can also be a detriment. A significant number of range forages such as serviceberry (Amelanchier alnifolia), bird's foot trefoil (Lotus corniculatus), chokeberry (Prunus virginiana), various sorghum species, white clover (Trifolium repens), and arrowgrass (Triglochin spp.) contain cyanogenic glycosides which are hydrolyzed during ruminal fermentation. These glycosides constitute a prominent class of toxic plant compounds (7, 9, 31) which presumably are synthesized to discourage grazing. For a review of the plant biosynthetic routes that produce these glycosides, see the work of Vennesland et al. (31).The P. ruminicola B 1 4 ␤-glucosidase catalyzes the first step in cyanide release from cyanogenic plant glycosides. Sin...

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Hydrolysis of the Cyanogenic Glycosides Amygdalin, Prunasin and Linamarin by Ruminal Microorganisms

Abstract: Three cyanogenic glycosides were incubated simultaneously but separately in rumen fluid from cattle to determine the rates of glycoside hydrolysis.

Cited by 21 publications

References 4 publications

Effectiveness of different processing methods in reducing hydrogen cyanide content of flaxseed

Effectiveness of different processing methods in reducing hydrogen cyanide content of flaxseed

The Rumen Microbial Ecosystem

Cloning, sequencing, and characterization of a membrane-associated Prevotella ruminicola B(1)4 beta-glucosidase with cellodextrinase and cyanoglycosidase activities

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