Rapoport S, Müller M, Dumdey R, Rathmann J
Eur J Biochem. 1980 Jul;108(2):449-55. doi: 10.1111/j.1432-1033.1980.tb04741.x.
In this work it is demonstrated the NH3 potentially available from the oxidation of amino acids by the reticulocyte is utilized for the new-synthesis of serine via transamination reactions with hydroxypyruvate and phosphohydroxypyruvate. These compounds are derived from glucose, which furnishes in this manner the carbon skeleton of serine. It was shown that serine is mainly degraded via glycine, while glycine is in the main formed from serine. Furthermore it was found that serine synthesis is localized in the cytosol, while the reversible transformation of serine to glycine takes place in the mitochondria. A transfer of methylenetetrahydrofolate occurs in both directions across the mitochondrial membrane. A concentrative uptake of serine by the mitochondria was found, while glycine is transported slowly in both directions. On the basis of the data an overall balance is given of the quantitative relations between protein breakdown and hemoglobin synthesis as well as for the new-formation and utilization of serine and glycine. The new-formation of serine may amount to about one tenth of the glucose utilized by the reticulocyte and furnishes about one-half of the serine and glycine moieties required for the synthesis of heme and globin. The remainder is provided by the energy-dependent protein breakdown.
在这项研究中，证明了网织红细胞通过氨基酸氧化产生的潜在氨，通过与羟基丙酮酸和磷酸羟基丙酮酸的转氨反应，用于丝氨酸的新合成。这些化合物来源于葡萄糖，葡萄糖以这种方式提供丝氨酸的碳骨架。结果表明，丝氨酸主要通过甘氨酸降解，而甘氨酸主要由丝氨酸形成。此外，发现丝氨酸合成定位于细胞质中，而丝氨酸向甘氨酸的可逆转化发生在线粒体中。亚甲基四氢叶酸在线粒体内膜两侧双向转移。发现线粒体对丝氨酸有浓缩摄取，而甘氨酸在两个方向上的转运都很慢。根据这些数据，给出了蛋白质分解与血红蛋白合成之间以及丝氨酸和甘氨酸的新形成与利用之间定量关系的总体平衡。丝氨酸的新形成量可能约为网织红细胞利用的葡萄糖的十分之一，并提供血红素和球蛋白合成所需的约一半的丝氨酸和甘氨酸部分。其余部分由能量依赖的蛋白质分解提供。
