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BIOCHEMICAL SOCIETY TRANSACTIONS
This study was supported by grant no. 71-2156 from the National Institutes of Health,
Bethesda, MD, U S A .
Blum, C. B., Levy, R. I . , Hall, M., Goebel, R. & Berman, M. (1976) Circulation54, Suppl. 11, 26
Eisenberg, S. & Levy, R. I. (1975) Adu. Lipid Res. 131, 1-89
Eisenberg, S., Bilheimer, D., Levy, R. I. & Lindgren, F. T. (1973) Biochim. Biophys. Acfa 326,
361-377
Grow, T. E. &Fried, M. (1977) Biochem. Biophys. Res. Commun. 75, 117-124
Krauss, R. M., Lindgren, F. T., Bradley, D. & Silvers, A. (1976) Circulation 54, Suppl. 11, 21 1
Patsch, J. R., Sailer, S., Kostner, G., Sandhofer, F., Holasek, A. & Braunsteiner, H. (1974)
J. Lipid Res. 15,356-366
Patsch, J. R., Yeshurun, D., Jackson, R. L. & Gotto, A. M. (1978) Am. J. Med. in the press
Scanu, A. M. & Wisdom, C. (1972) Annu. Rev.Biochem. 41,703-730
Shepherd, J., Gotto, A, M., Tauton, 0. D., Caslake, M. & Farish, E. (1978) Biochim. Biophys.
Acfa in the press
Identification of 5-Hydroxyhexanoic Acid in the Urine of Twin Siblings
with a Syndrome having Close Similarities to Jamaican Vomiting
Sickness
ALEXANDER M. LAWSON* and R O N A L D A. CHALMERSt
*Division of Clinical Chemistry and t Division of Inherited Metabolic Diseases,
Medical Research Council Clinical Research Centre, Watford Road, Harrow, Middx.
HA1 3UJ, U.K.
Jamaican vomiting sickness is characterized by sudden-onset acute vomiting and
diarrhoea with profound hypoglycaemia, leading t o coma and death. Pathological
changes observed include fatty infiltration of the viscera, and similarities with Reye’s
syndrome (encephalopathy and fatty degeneration of the viscera) have been noted
(Lowry, 1975). Recently, twin siblings presented in Harrow with a n unusual Reye’s-like
syndrome (Whitelaw et al., 1977) associated with an abnormal organic aciduria that had
similarities to that observed in patients with Jamaican vomiting sickness (Chalmers
et al., 1977), particularly in the nature of the dicarboxylic acids excreted (Chalmers &
Lawson, 1977). Jamaican vomiting sickness is caused by the ingestion by infants of
unripe ackee fruit, which contains the toxin hypoglycin (L-a-aminomethylenecyclopropylpropionic acid). The association of hypoglycin and Jamaican vomiting sickness
has been proved by the occurrence in the urine of two patients with the disease of the
glycine conjugate of the active metabolite of hypoglycin, methylenecyclopropylacetic
acid (Tanaka et al., 1976). The present paper reports the identification of 5-hydroxyhexanoic acid, a previously unreported urinary organic acid, in the urine of both Harrow
patients, which may indicate the underlying aetiology of these cases and the close
associations with Jamaican vomiting sickness.
Urine was obtained from both siblings on the day of admission to hospital (one urine
post mortem) and examined for organic acids by quantitative extraction techniques and
g.1.c. and mass spectrometry of the trimethylsilyl derivatives of the extracted acids.
Among the most prominent acids observed was one eluted at a retention time
relative to n-tetracosane internal standard of 0.39, in the region of organic acids such as
the 2,3-dihydroxybutanoic acids (Lawson et al., 1976). Initial low-resolution mass
spectrometry showed the acid to be unrecorded in the available library files of spectra
and excluded glutaric acid relative retention time 0.42) and ethylmalonic acid (relative
retention time0.37), which occur in the urine of patients with Jamaican vomiting sickness
(Tanaka et al., 1976). The molecular ion of the trimethylsilyl derivative was a t m/e 276,
and this was shown by high-resolution mass spectrometry to have the empirical formula
Ci2HZ803Si2
and hence be a monohydroxymonocarboxylic acid. Other prominent ions
1978
572nd MEETING, LONDON
109
I
(b)
I7
'i' '1'
i.;i ,I
,,I
lj; ,l;2,,,2]',
,,,,
I
245
I40
240
40
J-&J
ec,
245
I40
240
Fig. 1. Mass spectra of metabolite in urine (a) and authentic 5-hydroxyhexanoic acid (b)
I
CHJ-CH=CH-CH~-CH
CH-COzH
2-
I
NHz
2-Aminohept-5-enoic acid
I
CH~-CH=CH-CH~-CHZ-C-COZH
II
\
CHz=C-CH-CH
CH-C02H
2-
Hypoglycin
(L-a-aminomethylenecyclopropylpropionicacid)
CHZzC-
CH-CH2-C-CO2H
U
0
2-Oxohept-5-enoic acid
I
NHz
0
2-Oxomethylenecyclopropylpropionic acid
I
Leo,
Hex-Cenoyl-CoA
I
CH,-CH-CHz-CH,-CH,-COSR
b c o 2
Methylenecyclopropylacetyl-CoA
I
Methylenecyclopropylacetylglycine
I
OH
5-Hydroxyhexanoyl-CoA
J
5-Hydroxyhexanoic acid
Scheme 1. Metabolism of 2-aminohept-5-enoic acid and hypogiycin
Vol. 6
110
BIOCHEMICAL SOCIETY TRANSACTIONS
in the spectra (excluding m/e 73, which is common to all spectra of trimethylsilyl derivatives) were those at mle 261 (M-15), m/e 245 (M-31), m/e 232 (M -44), m/e 171
(M-15-90), m/e 117 (M-159), and of particular interest, m/e204(M-72), which was
considered to arise from long-range migration of OMe3Si, from a hydroxyl function
remote from the carboxylic function, on to the COzMe3Si group to give the ion
+
CH,=C-(OMe,Si).
OMe3Si. This indicated the possible structure as CH3-CH(OMe3Si)-[CHzl3-CO2Me3Si,
but other isomers (e.g. 4-hydroxy-3-methylpentanoic
acid, 4-hydroxy-2-methylpentanoicacid and 2-ethyl-3-hydroxybutanoicacid) could not
be excluded at this stage. Although the mass-spectrometric data were considered initially
to be most consistent with 4-hydroxy-2-methylpentanoicacid (Chalmers et al., 1976),
chemical synthesis of the possible isomers and comparison of their g.1.c. retention
data and low-resolution mass spectra (Fig. 1) conclusively proved the acid to be 5hydroxyhexanoic acid.
The occurrence of 5-hydroxyhexanoic acid in the urine of two patients in England with
a vomiting sickness having close clinical similarities to Jamaican vomiting sickness is of
great interest. Hypoglycin is metabolized by deamination and decarboxylation to its
active metabolite methylenecyclopropylacetyl-CoA (Tanaka et al., 1976) (Scheme 1).
The metabolic precursor of 5-hydroxyhexanoic acid could be hex-4-enoyl-CoA (Scheme
l), a close analogue of methylenecyclopropylacetyl-CoAand containing the -CH=CC-C-C02H
group that is apparently necessary in this class of compound for hypoglycaemic activity in animals. Preceding metabolic steps lead to 2-aminohept-5-enoic
acid, an analogue of hypoglycin itself. Hypoglycin analogues occur in a wide variety of
plant life (seeds and fruit) of common occurrence throughout the world, including those
of the Aceraceae (maple, sycamore) and Aesculus (horse chestnut) familes (Fowden,
1975). The close structural similarities between hex-4-enoic acid and 5-hydroxyhexanoic
acid, and sorbic (hexa-2,4-dienoicj acid and parasorbic (5-hydroxyhex-2-enoic)acid, both
of which occur in berries of mountain ash (rowan or Sorbus aucuparia L. ; Rosaceae), is
also of particular interest. Seeds and fruit of such common plants could easily be ingested
by infants, and although there is no evidence that this occurred in the present cases, their
original presentation in mid-autumn (1976) would support this hypothesis. Indeed, the
seasonal occurrence of Reye’s syndrome in infants and the presentation of the syndrome
would suggest that at least some cases may be due to the ingestion of seeds and fruit
containing toxic analogues of hypoglycin and their organic acid metabolites.
Chalmers, R. A. & Lawson, A. M. (1978) Biochem. SOC.Trans. 6, 111-113
Chalmers, R. A., Lawson, A. M., Whitelaw, A. & Purkiss, P. (1977)Lancet i, 1155-1156
Fowden, L. (1975) in Hypoglycin (Kean, E. A., ed.), pp. 11-19, Academic Press, New York
Lawson, A. M., Chalmers, R. A. &Watts, R. W. E. (1976) Clin. Gem. 22,1283-1287
Lowry, M. F. (1975) in Hypoglycin (Kean, E. A., ed.), pp. 45-50, Academic Press, New York
Tanaka, K., Kean, E. A. &Johnson, B. (1976) N . Engl. J . Med. 295,461-467
Whitelaw, A., Davies, H. & Parry, J. (1977) Lancet i, 361
1978