Shoolingin-Jordan Peter M, Al-Daihan Sooad, Alexeev Dmitriy, Baxter Robert L, Bottomley Sylvia S, Kahari I Donald, Roy Ipsita, Sarwar Muhammad, Sawyer Lindsay, Wang Shu-Fen
Biochemistry and Molecular Biology, School of Biological Sciences, The University of Southampton, Southampton, SO16 7PX, UK.
Biochim Biophys Acta. 2003 Apr 11;1647(1-2):361-6. doi: 10.1016/s1570-9639(03)00095-5.
5-Aminolevulinic acid synthase (ALAS), the first enzyme of the heme biosynthesis pathway, catalyses the pyridoxal 5'-phosphate-dependent condensation between glycine and succinyl-CoA to yield 5-aminolevulinic acid (5-amino-4-oxopentanoate). A three-dimensional structural model of Rhodobacter spheroides ALAS has been constructed and used to identify amino acid residues at the active site that are likely to be important for the recognition of glycine, the only amino acid substrate. Several residues have been investigated by site-directed mutagenesis and enzyme variants have been generated that are able to use alanine, serine or threonine. A three-dimensional structure model of 5-aminolevulinic acid synthase from human erythrocytes (ALAS 2) has also been constructed and used to map a range of naturally occurring human mutants that give rise to X-linked sideroblastic anemia. A number of these anemias respond favourably to vitamin B(6) (pyridoxine) therapy, whereas others are either partially responsive or completely refractory. Detailed investigations with selected human mutants have highlighted the importance of arginine-517 that is implicated in glycine carboxyl group binding.
5-氨基乙酰丙酸合酶（ALAS）是血红素生物合成途径的首个酶，催化磷酸吡哆醛依赖性的甘氨酸与琥珀酰辅酶A之间的缩合反应，生成5-氨基乙酰丙酸（5-氨基-4-氧代戊酸）。已构建球形红杆菌ALAS的三维结构模型，并用于鉴定活性位点处可能对唯一氨基酸底物甘氨酸的识别很重要的氨基酸残基。通过定点诱变研究了几个残基，并产生了能够使用丙氨酸、丝氨酸或苏氨酸的酶变体。也已构建人红细胞5-氨基乙酰丙酸合酶（ALAS 2）的三维结构模型，并用于绘制一系列导致X连锁铁粒幼细胞贫血的天然存在的人类突变体图谱。其中一些贫血对维生素B6（吡哆醇）治疗反应良好，而其他贫血则部分有反应或完全难治。对选定人类突变体的详细研究突出了与甘氨酸羧基结合有关的精氨酸-517的重要性。
