Rajaram V, Prasad K, Ratna Prasuna P, Ramachandra N, Bharath S R, Savithri H S, Murthy M R N
Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560 012, India.
Acta Crystallogr Sect F Struct Biol Cryst Commun. 2006 Oct 1;62(Pt 10):980-3. doi: 10.1107/S1744309106033884. Epub 2006 Sep 19.
Acetylornithine aminotransferase (AcOAT) is a type I pyridoxal 5'-phosphate-dependent enzyme catalyzing the conversion of N-acetylglutamic semialdehyde to N-acetylornithine in the presence of alpha-ketoglutarate, a step involved in arginine metabolism. In Escherichia coli, the biosynthetic AcOAT also catalyzes the conversion of N-succinyl-L-2-amino-6-oxopimelate to N-succinyl-L,L-diaminopimelate, one of the steps in lysine biosynthesis. It is closely related to ornithine aminotransferase. AcOAT was cloned from Salmonella typhimurium and E. coli, overexpressed in E. coli and purified using Ni-NTA affinity column chromatography. The enzymes crystallized in the presence of gabaculine. Crystals of E. coli AcOAT (eAcOAT) only diffracted X-rays to 3.5 A and were twinned. The crystals of S. typhimurium AcOAT (sAcOAT) diffracted to 1.9 A and had a dimer in the asymmetric unit. The structure of sAcOAT was solved by the molecular-replacement method.
乙酰鸟氨酸转氨酶（AcOAT）是一种I型依赖磷酸吡哆醛的酶，在α-酮戊二酸存在的情况下催化N-乙酰谷氨酸半醛转化为N-乙酰鸟氨酸，这是精氨酸代谢中的一个步骤。在大肠杆菌中，生物合成的AcOAT还催化N-琥珀酰-L-2-氨基-6-氧代庚二酸转化为N-琥珀酰-L,L-二氨基庚二酸，这是赖氨酸生物合成中的一个步骤。它与鸟氨酸转氨酶密切相关。AcOAT从鼠伤寒沙门氏菌和大肠杆菌中克隆出来，在大肠杆菌中过表达，并使用镍-氮三乙酸亲和柱色谱法进行纯化。这些酶在加巴喷丁存在的情况下结晶。大肠杆菌AcOAT（eAcOAT）的晶体仅能将X射线衍射到3.5埃，并且存在孪晶现象。鼠伤寒沙门氏菌AcOAT（sAcOAT）的晶体衍射到1.9埃，并且在不对称单位中有一个二聚体。sAcOAT的结构通过分子置换法解析出来。
