The remethylation of homocysteine to methionine is important for chick embryos to sustain the S‐adenosylmethionine transmethylation reactions, which are essential for the rapid proliferation of cells. Developmental changes in hepatic 5‐methyltetrahydrofolate‐homocysteine methyltransferase (MFMT), betaine‐homocysteine methyltransferase (BHMT) and hepatic serine hydroxymethyltransferase (SHMT) were determined in E10‐21 Cobb 500 broiler chick embryos and hatched chicks from D1‐49. Hepatic levels of free serine, glycine, putrescine, spermidine and spermine levels were also determined. Analyses showed hepatic MFMT‐specific activity doubled from E10 to E12, with remaining embryo development experiencing small fluctuations in activity through E21. Hepatic MFMT doubled immediately after hatch, with peak activity occurring at D3. Afterwards, hepatic MFMT‐specific activity steadily declined from D7‐49. Hepatic BHMT activity was higher from E10 to E16 of embryogenesis, decreased rapidly at E17 and remained lower through E21 (p < .05). Hepatic BHMT‐specific activity was also lower in chicks, with the exception of a peak in specific activity on D7. BHMT activity returned to lower levels by D21. Throughout embryogenesis, hepatic SHMT activity in chick embryos remained relatively constant except for a decrease at 13E, followed by an increase at 14E. Maximal activity of SHMT was found the first day post‐hatch. Additionally, SHMT activity was significantly lower in growing chicks than that in embryos. Hepatic‐free serine and glycine levels were negatively correlated with SHMT in hatched chicks. Hepatic polyamine, putrescine and spermidine shared a similar development pattern: peak level in the middle of incubation, low at late embryogenesis and lowest during the post‐hatch period except an increase within one week after hatch. The sharp increase in hepatic concentrations of glycine, serine and putrescine, along with increased specific activities of MHMT, BHMT and SHMT from D1‐7, suggests that methionine conservation (remethylation from homocysteine) and glycine/serine is critical for young chicks for organ growth, maturation, and development.

中文翻译：

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E10-21 鸡胚和 D1-49 肉鸡生理氨基酸和肝蛋氨酸再甲基化酶活性的发育变化。

同型半胱氨酸再甲基化为甲硫氨酸对于鸡胚胎维持 S-腺苷甲硫氨酸转甲基反应很重要，这对于细胞的快速增殖至关重要。在 D1-49 的 E10-21 Cobb 500 肉鸡胚胎和孵化的小鸡中测定了肝脏 5-甲基四氢叶酸-高半胱氨酸甲基转移酶 (MFMT)、甜菜碱-高半胱氨酸甲基转移酶 (BHMT) 和肝脏丝氨酸羟甲基转移酶 (SHMT) 的发育变化。还测定了游离丝氨酸、甘氨酸、腐胺、亚精胺和精胺水平的肝脏水平。分析表明，肝脏 MFMT 特异性活性从 E10 到 E12 翻了一番，剩余的胚胎发育通过 E21 经历了活性的小波动。孵化后肝脏 MFMT 立即翻倍，活动峰值出现在 D3。然后，肝脏 MFMT 特异性活性从 D7-49 开始稳步下降。肝脏 BHMT 活性从胚胎发生的 E10 到 E16 较高，在 E17 迅速下降，并通过 E21 保持较低。磷 < .05）。小鸡的肝脏 BHMT 特异性活性也较低，除了 D7 时的特异性活性峰值。到 D21，BHMT 活性恢复到较低水平。在整个胚胎发生过程中，鸡胚胎中的肝 SHMT 活性保持相对稳定，除了在 13E 降低，然后在 14E 增加。孵化后第一天发现 SHMT 的最大活性。此外，生长雏鸡的 SHMT 活性显着低于胚胎。在孵化的小鸡中，肝游离丝氨酸和甘氨酸水平与 SHMT 呈负相关。肝多胺、腐胺和亚精胺具有相似的发育模式：孵化中期达到峰值，胚胎发生后期低，孵化后最低，孵化后一周内增加。