The origin of alanine produced in skeletal muscle.
The origin of alanine produced in skeletal muscle.
复制标题
骨骼肌中产生的丙氨酸的来源。
DOI：
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发表时间：
1978
影响因子：
4.8
通讯作者：
A. Goldberg
中科院分区：
文献类型：
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作者：
T. Chang;A. Goldberg
进行这些研究是为了阐明骨骼肌大量释放丙氨酸的来源。亮氨酸，生酮氨基酸，以及异亮氨酸和缬氨酸，这是葡萄糖，增加谷氨酸的细胞内浓度和刺激生产的丙氨酸和谷氨酰胺通过离体大鼠横膈膜。这些氨基酸的转氨作用程度（即环酮酸脱羧和积累的总和）等于丙氨酸、谷氨酰胺和谷氨酸的总增加。因此，支链氨基酸可以刺激丙氨酸和谷氨酰胺生产简单地通过提供氨基与cY-酮戊二酸转氨。提供0.3mM NH 2+增加了谷氨酰胺的产生，因为谷氨酸向谷氨酰胺的转化更大。细胞谷氨酸浓度的下降可以解释丙氨酸产生的相关减少。丙氨酸和谷氨酰胺的生产受到碳链和氨基供应的限制。葡萄糖刺激大鼠膈肌产生丙氨酸。当肌肉也提供支链氨基酸时，刺激更大。此外，Z-脱氧葡萄糖，抑制糖酵解，减少丙氨酸的生产。碘乙酸盐和氟化物也降低丙氨酸和乳酸盐的产生。然而，观察与后者抑制剂（不像那些与2-脱氧葡萄糖）是复杂的，因为他们也减少转氨抑制支链氨基酸的氧化脱羧，同时促进净蛋白质分解。肌肉蛋白质中的大多数氨基酸被认为是丙氨酸和谷氨酰胺中碳的来源。然而，用隔膜、比目鱼肌和趾长伸肌进行的实验表明，只有某些1%标记的氨基酸可以转化为“CO2”。其中，只有五种氨基酸，天冬氨酸，天冬酰胺，谷氨酰胺，异亮氨酸和缬氨酸被转化为三羧酸循环中间体，并且只有这些氨基酸可能为丙氨酸或谷氨酰胺提供碳骨架。这五种氨基酸的生成速率
These studies were undertaken to clarify the origin of alanine released in large amounts by skeletal muscle. Leutine, a ketogenic amino acid, as well as isoleucine and valine, which are glucogenic, increased the intracellular concentration of glutamate and stimulated the production of alanine and glutamine by isolated rat diaphragms. The extent of transamination of these amino acids (i.e. the sum of cy-keto acid decarboxylation and accumulation) equalled the total increase in alanine, glutamine, and glutamate. Thus the branched-chain amino acids may stimulate alanine and glutamine production simply by supplying amino groups for transamination with cY-ketoglutarate. Providing 0.3 mM NH,+ increased glutamine production because of greater conversion of glutamate to glutamine. The fall in cellular glutamate concentration can explain the associated decrease in alanine production. The production of alanine and glutamine is limited by the supply of carbon chains as well as amino groups. Glucose stimulated alanine production by rat diaphragms. The stimulation was larger when the muscle was also provided with branched-chain amino acids. In addition, Z-deoxyglucose, which inhibited glycolysis, reduced alanine production. Iodoacetate and fluoride also decreased alanine and lactate production. However, observations with the latter inhibitors (unlike those with 2-deoxyglucose) are complicated because they also decreased transamination by inhibiting the oxidative decarboxylation of branched-chain amino acids and simultaneously promoted net protein breakdown. Most of the amino acids in muscle protein have been suggested as sources of the carbons in alanine and glutamine. Experiments with diaphragm, soleus, and extensor digitorum longus, however, showed that only certain I%labeled amino acids could be converted to “C02. Of these, only five amino acids, aspartate, asparagine, glutamine, isoleucine, and valine are converted to tricarboxylic acid cycle intermediates, and only these amino acids could possibly supply the carbon skeleton for alanine or glutamine. The rate of generation of these five amino acids by the net