Threonine metabolism in isolated rat hepatocytes

House, James D.; Hall, Beatrice; Brosnan, John T.

doi:10.1152/ajpendo.2001.281.6.e1300

Cited by 47 publications

(37 citation statements)

References 31 publications

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“…Although the two enzymes have similar Km values, the maximal activity of TDH is lower than that of SDH. In isolated rat hepatocytes approximately 65% of threonine oxidation occurs through the threonine dehydratase pathway [15]. A similar situation is found in humans where the TDH pathway accounts for only 7-11% of total threonine catabolism [16].…”

Section: Discussionsupporting

confidence: 54%

The effect of dietary protein on the amino acid supply and threonine metabolism in the pregnant rat

Rees¹,

Hay²,

Antipatis³

2006

Reprod. Nutr. Dev.

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-To characterise the effects of dietary protein content on threonine metabolism during pregnancy, rats were fed diets containing 18% or 9% protein and then killed at different stages of gestation. Serum threonine concentrations fell significantly faster in the animals fed the diet containing 9% protein when compared to those fed the diet containing 18% protein. On day 4 of gestation the rate of threonine oxidation was higher in maternal liver homogenates prepared from the animals fed the diet containing 18% protein. The rate of threonine oxidation by liver homogenates fell as gestation proceeded in both diet groups. The activity of threonine dehydrogenase in the maternal liver was unaffected by dietary protein content at all stages of gestation. Serine-threonine dehydratase activity in homogenates of the maternal liver was transiently increased during the early stages of gestation in the animals fed high protein diets but was unchanged in the low protein groups. There was an increase in serine-threonine dehydratase activity in the kidney during the later stages of gestation but this was unaffected by the protein content of the maternal diet. These data show that the changes in free threonine concentrations cannot be accounted for through changes in the oxidation rate and suggest that some other factor influences the unusual metabolism of this amino acid during gestation. threonine dehydratase / threonine dehydrogenase / protein metabolism / pregnancy / foetus / metabolic programming Abbreviations: SDH, serine/threonine dehydratase; TDH, threonine dehydrogenase; PCA, perchloric acid; TCA, trichloroacetic acid.

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Section: Discussionsupporting

confidence: 54%

The effect of dietary protein on the amino acid supply and threonine metabolism in the pregnant rat

Rees¹,

Hay²,

Antipatis³

2006

Reprod. Nutr. Dev.

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“…Segundo House et al (2001), a oxidação de treonina pode ser classificada em duas vias distintas: glicina dependente (treonina desidrogenase e treonina aldolase) e glicina independente (treonina desidratase). Entretanto, para todas as enzimas envolvidas no catabolismo de treonina, houve redução da atividade com a adição de glicina à dieta.…”

Section: Resultsunclassified

“…A redução da atividade da degradação de treonina pela via dependente de glicina também foi observada por House et al (2001) em estudo no qual avaliaram a produção de 14 CO 2 utilizando treonina com 14 C na posição 1 em hepatócitos de ratos. Quando os hepatócitos foram incubados com cisteamina (inibidor da clivagem de glicina), houve redução de 24% da produção de 14 CO 2 .…”

Section: Resultsunclassified

Efeito de diferentes relações treonina: lisina digestíveis, suplementadas ou não com glicina, sobre a atividade enzimática em pintos de corte

Bernardino¹,

Albino²,

Rostagno³

et al. 2011

R. Bras. Zootec.

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RESUMO -O experimento foi conduzido com o objetivo de avaliar o efeito da suplementação de glicina em dietas com diferentes relações treonina:lisina digestíveis sobre a atividade de enzimas que metabolizam a treonina. Foram utilizados 560 pintos de corte machos, linhagem Cobb, durante o período de 8 a 21 dias de idade, distribuídos em delineamento inteiramente casualizado, num arranjo fatorial 3 × 2 + 1, composto de três relações treonina:lisina digestíveis (55; 65 e 75%), com suplementação ou não de glicina, mais um tratamento adicional, contendo farinha de carne e ossos e com relação treonina:lisina digestíveis de 65%. Utilizaram-se oito repetições por tratamento e 10 aves por unidade experimental alojadas em baterias metálicas. Procedeu-se à coleta total de excretas durante toda a fase experimental. Para determinação da atividade das enzimas treonina aldolase, treonina desidrogenase e treonina desidratase, foram abatidas no final do experimento duas aves por unidade experimental para retirada do fígado. As relações treonina:lisina influenciaram a atividade das três enzimas no fígado: a maior atividade de treonina aldolase foi para a relação de 75%; a de treonina desidrogenase para a relação de 65%, e a de treonina desidratase para a relação de 55%. A suplementação de glicina reduz a atividade de todas as enzimas avaliadas.Palavras-chave: treonina aldolase, treonina desidratase, treonina desidrogenase Effect of different digestible threonine:digestible lysine ratios, with or without glycine supplementation, on the enzymatic activity in broiler chicks ABSTRACT -The experiment was conducted with the objective evaluating the effect of supplementation of glycine in diets with different digestible threonine:digestible lysine ratios on the activity of enzymes that metabolize threonine. Five hundred and sixty male broiler chicks from the Cobb strain were used during the period of 8 to 21 days, distributed in a completely randomized design, in a 3 × 2 + 1 factorial arrangement, with 3 digestible threonine:digestible lysine ratios (55; 65 and 75%), with or without supplementation of glycine, plus an additional treatment, containing meat and bone meal, with a 65% digestible threonine:digestible lysine ratio. Eight repetitions were used per treatment and 10 birds per experimental unit, allotted in metal battery cages. The total excreta collection was performed throughout the whole experimental stage. For the determination of the activity of the threonine aldolase, threonine dehydrogenase and threonine dehydratase enzymes, at the end of the experiment, two birds were slaughtered and had their livers extracted. The threonine:lysine ratios influenced the activity of the three enzymes in the liver; while the greatest activity of the threonine aldolase was for the ratio of 75%, for threonine dehydrogenase it was 65%, and for the threonine dehydratase it was 55%. Supplementation of glycine reduced the activity of all enzymes evaluated.

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“…Only one of the three threonine degradation pathways produces glycine (threonine dehydrogenase and glycine C-acetyl transferase [TDH-GAT]) as threonine aldolase (TAL) is inactive in mammals. These fl uxes have been assayed in human metabolism in vivo by several authors, and there is a general agreement that threonine is a poor source of glycine (Yeung 1986;Parimi et al 2005), and no more than 7% of the threonine catabolized is converted to glycine (House et al 2001). The recommended regular intake of threonine (FAO/WHO/UNU 1985) for a 70 kg human adult is 490 mg (4.1 mmol) per day, and 7% of this (0.3 mmol) is the daily production of glycine in this pathway.…”

Section: Synthesis Of Glycine Independent Of Glycine Hydroxymethyltramentioning

confidence: 99%

A weak link in metabolism: the metabolic capacity for glycine biosynthesis does not satisfy the need for collagen synthesis

Meléndez-Hevia¹,

Paz-Lugo²,

Cornish‐Bowden

et al. 2009

J Biosci

110

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In a previous paper, we pointed out that the capability to synthesize glycine from serine is constrained by the stoichiometry of the glycine hydroxymethyltransferase reaction, which limits the amount of glycine produced to be no more than equimolar with the amount of C 1 units produced. This constraint predicts a shortage of available glycine if there are no adequate compensating processes. Here, we test this prediction by comparing all reported fl uxes for the production and consumption of glycine in a human adult. Detailed assessment of all possible sources of glycine shows that synthesis from serine accounts for more than 85% of the total, and that the amount of glycine available from synthesis, about 3 g/day, together with that available from the diet, in the range 1.5-3.0 g/day, may fall significantly short of the amount needed for all metabolic uses, including collagen synthesis by about 10 g per day for a 70 kg human. This result supports earlier suggestions in the literature that glycine is a semi-essential amino acid and that it should be taken as a nutritional supplement to guarantee a healthy metabolism.

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Threonine metabolism in isolated rat hepatocytes

Cited by 47 publications

References 31 publications

The effect of dietary protein on the amino acid supply and threonine metabolism in the pregnant rat

The effect of dietary protein on the amino acid supply and threonine metabolism in the pregnant rat

Efeito de diferentes relações treonina: lisina digestíveis, suplementadas ou não com glicina, sobre a atividade enzimática em pintos de corte

A weak link in metabolism: the metabolic capacity for glycine biosynthesis does not satisfy the need for collagen synthesis

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