The biosynthesis of trimethylamine-N-oxide

“…A radioisotopic assay was developed, based on the assay of Baker and Chaykin (Baker and Chaykin, 1962), to determine the TMAoxi activity of liver homogenates. The assay conditions were as follows: 50·mmol·l -1 Tris (pH·8.5), 50·mmol·l -1 KCl, 0.3·mmol·l -1 NADPH, 1.0·mmol·l -1 TMA including […”

Section: Enzyme Activitiesmentioning

confidence: 99%

The accumulation of methylamine counteracting solutes in elasmobranchs with differing levels of urea: a comparison of marine and freshwater species

Treberg

Speers‐Roesch

Piermarini

et al. 2006

Journal of Experimental Biology

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SUMMARY We compared levels of the major organic osmolytes in the muscle of elasmobranchs, including the methylamines trimethylamine oxide (TMAO), betaine and sarcosine as well as the β-amino acids taurine and β-alanine,and the activities of enzymes of methylamine synthesis (betaine and TMAO) in species with a wide range of urea contents. Four marine, a euryhaline in freshwater (Dasyatis sabina), and two freshwater species, one that accumulates urea (Himantura signifer) and one that does not(Potamotrygon motoro), were analyzed. Urea contents in muscle ranged from 229–352 μmol g–1 in marine species to 2.0μmol g–1 in P. motoro. Marine elasmobranchs preferentially accumulate methylamines, possibly to counteract urea effects on macromolecules, whereas the freshwater species with lower urea levels accumulate the β-amino acid taurine as the major non-urea osmolyte. A strong correlation (r2=0.84, P<0.001) with a slope of 0.40 was found between muscle urea content and the combined total methylamines plus total β-amino acids, supporting the hypothesis that`non-urea' osmolytes are specifically maintained at an approximately 2:1 ratio with urea in the muscle of elasmobranchs. All species examined had measurable synthetic capacity for betaine in the liver but only one species had detectable TMAO synthetic capacity. We propose a phylogenetic explanation for the distribution of TMAO synthesis in elasmobranchs and suggest that activation of liver betaine aldehyde dehydrogenase, relative to choline dehydrogenase, coincides with betaine accumulation in elasmobranchs. The latter relationship may be important in maintaining methylamine levels during periods of low dietary TMAO intake for species lacking TMAO synthesis.

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“…MMA and TMA can be metabolized to DMA to a small extent (Asatoor and Simenhoff, 1965). TMA is oxidized by a specific enzyme, trimethylamine oxidase (Baker and Chaykin, 1962), and MMA is oxidized by semicarbazide-sensitive amine oxidase (Lyles and McDougall, 1989) and plasma amine oxidase (McEwan, 1965).…”

Section: Introductionmentioning

confidence: 99%

Developmental toxicity of methylamines in mice

Guest

Varma

1991

Journal of Toxicology and Environmental Health

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Monomethylamine (MMA), dimethylamine (DMA), and trimethylamine (TMA) are endogenous substances as well as metabolites of methyl isocyanate, the chemical involved in the 1984 accident at Bhopal, India. Although methylamines exert several toxic effects including inhibition of protein turnover and oocyte RNA synthesis, their reproductive toxicity has not been investigated. We therefore studied the possible developmental toxicity of these amines using pregnant CD-1 mice and mouse embryo culture as experimental models. Intraperitoneal injections (daily from d 1 to 17 of gestation) of TMA at 2.5 and 5 mmol/kg/d significantly (p less than .001) decreased fetal body weight but not the placental weight or maternal body weight gain; however, 5 of 11 mice treated with 5 mmol/kg TMA died. Similar treatment with DMA and MMA did not exert any obvious maternal or fetal effects. All three methylamines, when added to embryos in culture, caused dose-dependent decreases in size, DNA, RNA, and protein content as well as embryo survival; the order of toxicity was TMA greater than DMA greater than MMA. The ability of methylamines to adversely affect fetal development suggests that these amines, especially trimethylamine, may act as endogenous teratogens under certain conditions.

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The biosynthesis of trimethylamine-N-oxide

Cited by 56 publications

References 9 publications

TMAO: A small molecule of great expectations

TMAO: A small molecule of great expectations

The accumulation of methylamine counteracting solutes in elasmobranchs with differing levels of urea: a comparison of marine and freshwater species

Developmental toxicity of methylamines in mice

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