D-Threonine aldolase is an enzyme belonging to the glycine-dependent aldolases, and it catalyzes the reversible aldol reaction of glycine and acetaldehyde to give D-threonine and/or D-allo-threonine. In this study, a putative D-threonine aldolase gene from Delftia sp. RIT313 was cloned and expressed in Escherichia coli BL21 (DE3). The purified enzyme (DrDTA, 47 KDa) exhibited 21.3 U mg−1 activity for the
d -苏氨醛缩酶是属于甘氨酸依赖性醛缩酶的酶,它催化甘氨酸和乙醛,得到的可逆醛醇缩合反应d -苏氨酸和/或d -异体-苏氨酸。在这项研究中,来自Delftia sp。的一个推定的D-苏氨酸醛缩酶基因。RIT313被克隆并在大肠杆菌BL21(DE3)中表达。纯化的酶(DrDTA,47 KDa)表现出21.3 U mg -1在50°C的MES-NaOH缓冲液(pH 6.0)中添加甘氨酸和乙醛的醛醇缩合酶的活性。反应需要吡ido醛5'-磷酸和金属离子,并且金属离子的存在增强了酶的稳定性。结果发现,转化和C β -stereoselectivity受到显着受反应温度,助溶剂,酶和反应时间的量的影响,并且能够以使动力学控制下进行反应,以保持在合适的转化率和高立体选择性β-碳,从而解决了“ Cβ-立体选择性问题”。DrDTA对具有吸电子取代基的芳族醛显示出高活性。在优化的反应条件下,获得具有2'-氟或
Synthesis of β-hydroxy-α-amino acids with a reengineered alanine racemase
作者:Kateryna Fesko、Lars Giger、Donald Hilvert
DOI:10.1016/j.bmcl.2008.08.031
日期:2008.11
ino acids. It promotes the PLP-dependent aldol condensation of glycine with a range of aromatic aldehydes. The desired products were obtained with complete stereocontrol at C(alpha) (ee>99%, D) and moderate to high selectivity at C(beta) (up to 97% de). The designed enzyme is thus similar to natural d-threonine aldolases in its substrate specificity and stereoselectivity. Moreover, its ability to utilize
A directaldolreaction of an α‐azido 7‐azaindolinylamide, promoted by a Cu‐based cooperative catalyst, is documented. Aromatic aldehydes bearing an ortho substituent exhibited diastereodivergency depending on the nature of the chiral ligands used. Smooth reactions with ynals highlighted the broad substrate scope. A vicinal azido alcohol unit in the product allowed direct access to the corresponding