Hypoglycin is a naturally occurring organic compound in the species Blighia sapida. It is particularly concentrated in the fruit of the plant. Hypoglycin is toxic if ingested and is the causative agent of Jamaican Vomiting Sickness

Jamaican vomiting sickness

Jamaican vomiting sickness is an acute illness caused by the toxin hypoglycin A, which is present in unripened fruit of the ackee tree. Hypoglycin A is present in the unripe arilli at levels of over 1000 ppm, which falls to less than 0.1 ppm in the fully ripened arilli. Hypoglycin B, found only...

. It is an amino acid

Amino acid

Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...

 and chemically related to lysine

Lysine

Lysine is an α-amino acid with the chemical formula HO2CCH4NH2. It is an essential amino acid, which means that the human body cannot synthesize it. Its codons are AAA and AAG....

. It competitively binds to enzymes used in the catabolism of lysine and is the reason why it and its metabolite MCPA (methylene cyclopropyl acetic acid) are toxic.

The metabolite MCPA also is a potent inhibitor of Acyl-CoA dehydrogenase, preventing the metabolism of fatty acids. The symptoms of Hypoglycin-A ingestion are intolerance to prolonged fasting (due to inability to switch from glucose to fatty acid oxidation), impaired ketogensis, vomiting, lethargy, unconsciousness, coma, death, and increased urinary excretion of dicarboxylic acid

Dicarboxylic acid

Dicarboxylic acids are organic compounds that contain two carboxylic acid functional groups. In molecular formulae for dicarboxylic acids, these groups are often written as HOOC-R-COOH, where R may be an alkyl, alkenyl, alkynyl, or aryl group...

, due to omega oxidation that occurs in the ER.