[Mephistopheles]

Cyanamide is used for decades as fertilizer and pesticide/herbicide; I understand how it liberates nitrogen (serving as fertiliser) yet the chemical reason for its toxicity is unclear to me. What exactly does it do on a biochemical level? Or is it probably the ammonia, that is generated when it decomposes, that exerts the toxic action?

[AWK]

This is a simple two step hydrolysis reaction. Ammonia is liberated
H₂NCN + H₂O = H₂NCONH₂ (urea)
H₂NCONH₂ + H₂O = 2NH₃ + CO₂ (NH₂CO₂^-NH₄⁺)

[Yggdrasil]

I'm not sure the hydrolysis would be a factor since urea is fairly stable in the body and does not liberate ammonia (in fact, the body uses urea as a means to get rid of ammonia).

[AWK]

What ureases do?

[Yggdrasil]

Ureases liberate ammonia from urea, but these enzymes are not made by the human body. 

[Mephistopheles]

1. my question was, WHAT exactly causes the toxicity of cyanamide to cells (NOT: if it liberates ammonia, that is fairly sure). 2. The questions was not specifically on toxicity to humans, but more general to cells.
So - is it the ammonia that makes cyanamide toxic?

[AWK]

http://www.osha.gov/SLTC/healthguidelines/cyanamide/recognition.html

[Mephistopheles]

thanks -but, again: it does not answer my questions.
What makes cyanamide a toxin on a cellular level (I am NOT asking for the toxicity to humans), but which biochemical mechanisms are involved mto make it a good fungicide, herbizide, et cetera?

[dave14]

Sorry for necro-posting, but if I can stumble upon this post, so can anyone else. The term: exactly, referring to biology is a bit extreme. But, suffice it to say, hydrogen cyanamide is a acetylaldehyde dehydrogenase antagonist, so it causes a buildup of acetylaldehyde in animals that employ the enzyme. Acetylaldehyde is a destructive pollutant used in industrial manufacturing. It is CH3CHO, or MeCHO, because CH3 is a Methyl group. It is classified as a VOC. It is also produced by metabolism of ethyl alcohol. Hydrogen cyanamide is quite deadly in small amounts when consumed concurrent to beverage alcohol. It is also used in JaPAN
as a drug for alcohol-aversion therapy.

Chronic poisoning causes multiple organ damage, necessitating years of medical treatment.   

   

[Babcock_Hall]

The exact mechanism is not known, but metabolic acidosis is one of the symptoms.  What is the reason for your curiosity?

[Babcock_Hall]

"Animal studies have indicated that at cellular level, cyanamide is activated by catalase, which in turn causes catalase inhibition resulting in uncoupling of oxidation and phosphorylation and inhibition of adenosine nucleotide synthesis.[9]"
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3162724/