Glycine biosynthesis

The proteinogenic amino acid glycine can biosynthesized via several different pathways. The main pathway in most organisms is the production of glycine from L-serine via EC 2.1.2.1, glycine hydroxymethyltransferase. Eukaryotic organisms have both a cytosolic enzyme (SHMT2) and a mitochondrial enzyme (SHMT1) (see glycine biosynthesis I). The two isoforms were reported to work in opposite directions depending on the culture conditions. In a third pathway glycine is formed from glyoxylate, a product of the glyoxylate cycle, by the enzyme EC 2.6.1.44, alanine—glyoxylate transaminase (see glycine biosynthesis III). And finally, glycine can also be formed from L-threonine by the action of EC 4.1.2.48, low-specificity L-threonine aldolase (see glycine biosynthesis IV). Description adapted from https://pathway.yeastgenome.org/.

蛋白质合成氨基酸甘氨酸可通过多种不同的途径生物合成。在大多数生物体中，甘氨酸的主要合成途径为通过EC 2.1.2.1编号的甘氨酸羟甲基转移酶，由L-丝氨酸生成。真核生物体中存在胞质酶（SHMT2）和线粒体酶（SHMT1）（参见甘氨酸生物合成I）。据报道，这两种同工酶在培养条件不同的情况下表现出相反的作用方向。在第三条途径中，甘氨酸由甘露醇酸循环的产物甘露醇酸通过EC 2.6.1.44编号的丙氨酸-甘露醇酸转氨酶形成（参见甘氨酸生物合成III）。最后，甘氨酸还可以通过EC 4.1.2.48编号、低特异性的L-苏氨酸醛缩酶的作用，从L-苏氨酸生成（参见甘氨酸生物合成IV）。描述摘自https://pathway.yeastgenome.org/。