The synthesis of trimethilamine from choline in rat liver
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Endogenous trimethylamine (TMA) synthesis was investigated in rat tissues in vitro. Muscle or kidney homogenate did not demonstrate any ability to synthesize trimethylamine or trimethylamine oxide (TMAO) from choline. However, liver homogenate did make TMA and TMAO from choline. This reaction was not due to bacterial conversion of choline since aseptic preparation and incubation of liver homogenate produced similar amounts of TMA. TMA synthesis from choline in liver subcellular fractions was then investigated. This phenomenon was found to be associated with the mitochondrial fraction. The direct precursor for this reaction was investigated. TMAO, or betaine were not precursors for TMA. Betaine aldehyde, an oxidation product of choline, made more TMA than did choline. Phosphocholine produced some TMA but it was not as good a precursor as was choline or betaine aldehyde. Choline oxidase inhibitors, rotenone and low oxygen, both inhibited TMA synthesis from choline. This suggests that choline oxidase, possibly via formation of betaine aldehyde, is involved in the conversion of choline to TMA. This work demonstrates, for the first time, the existence of a pathway for TMA synthesis in mammals. The author suggests choline as the precursor for this reaction via betaine aldehyde. This reaction is carried out in two steps. First, choline aldehyde dehydrogenase, in liver mitochondria, converts choline to betaine aldehyde. Second, betaine aldehyde is then converted to TMA.
PLEASE NOTE: This work is protected by copyright. Downloading is restricted to the BU community: please click Download and log in with a valid BU account to access. If you are the author of this work and would like to make it publicly available, please contact email@example.com.Includes photographs.Thesis (D.Sc.D.)--Boston University, Henry M. Goldman School of Graduate Dentistry, 1989 (Nutritional Sciences.Bibliography : leaves 88-98.
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