Threonine is catabolized by L-threonine 3-dehydrogenase and threonine dehydratase in hepatocytes from domestic cats (Felis domestica)
Threonine is catabolized by L-threonine 3-dehydrogenase and threonine dehydratase in hepatocytes from domestic cats (Felis domestica)
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DOI：
10.1093/jn/126.9.2218
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发表时间：
1996-09-01
影响因子：
4.2
通讯作者：
Freedland, RA
中科院分区：
文献类型：
--
作者：
Hammer, VA;Rogers, QR;Freedland, RA
使用分离的肝细胞来研究小猫的苏氨酸分解代谢，并改变饮食中的苏氨酸和粗蛋白来研究酶的适应。细胞是从 21 周龄的小猫中分离出来的，这些小猫的饮食中含有 4 或 8 g/kg 苏氨酸，以及 200 或 500 g 粗蛋白/kg 饮食（2 x 2 阶乘，n = 4/组）。测量了 [U-C-14] 苏氨酸产生的 CO2、葡萄糖和各种代谢物。在孵育培养基中加入 10 mmol/L 甘氨酸或甘氨酸与 10 mmol/L 乙醛 + 乙醇组合可减少 (CO2)-C-14 和 [C-14] 葡萄糖的形成。同时，形成大量的[C-14]甘氨酸，但没有形成[C-14]乙醇。加入 10 mmol/L 2-酮丁酸 + 2-羟基丁酸会减少 (CO2)-C-14，但不会减少 [C-14] 葡萄糖的产生，并导致 [C-14]2-羟基丁酸的形成。在所有培养条件下，(CO2)-C-14 和 [C-14] 葡萄糖产量随着膳食蛋白质的变化而变化，但膳食苏氨酸的变化却没有变化。苏氨酸脱水酶和 L-苏氨酸 3-脱氢酶（而非苏氨酸醛缩酶）似乎是猫苏氨酸代谢的活跃途径，并且这两种酶对膳食蛋白质水平敏感。
Isolated hepatocytes were used to study threonine catabolism in kittens, and dietary threonine and crude protein were varied to study enzyme adaptation. Cells were isolated from 21-wk-old kittens which had been fed diets containing threonine at 4 or 8 g/kg of diet with either 200 or 500 g crude protein/kg of diet (2 x 2 factorial, n = 4/group). Production of CO2, glucose and various metabolites from [U-C-14]threonine were measured. Inclusion of 10 mmol/L glycine, or glycine in combination with 10 mmol/L acetaldehyde + ethanol, in the incubation medium decreased formation of (CO2)-C-14 and [C-14]glucose. At the same time, large amounts of [C-14]glycine but no [C-14]ethanol was formed. Inclusion of 10 mmol/L 2-ketobutyrate + 2-hydroxybutyrate decreased (CO2)-C-14 but not [C-14]glucose production and resulted in the formation of [C-14]2-hydroxybutyrate. Under all incubation conditions, (CO2)-C-14 and [C-14]glucose production changed in response to alterations in dietary protein but not dietary threonine. It appears that threonine dehydratase and L-threonine 3-dehydrogenase, but not threonine aldolase, are active pathways for threonine metabolism in cats, and both enzymes are sensitive to levels of dietary protein.