106819-03-8Relevant articles and documents
Total Asymmetric Transformations at Interfaces with Centrosymmetric Cristals: Role of Hydrophobic and Kinetic Effects in the Crystallization of the System Glycine/α-Amino Acids
Weissbuch, I.,Addadi, L.,Leiserowitz, L.,Lahav, M.
, p. 561 - 567 (1988)
A model of generation and amplification of optical activity, using the centrosymmetric crystals of glycine as substrates for total separation of occluded α-amino acids into enantiomeric territories, is described.The principle is based on the enantioselective occlusion of these additives through the enantiotopic (010) and (00) faces of glycine cristals.Such crystals, when floating at the air/solution interface, and if correctly oriented, may incorporate only one of the two enantiomeric additives present in solution.We demonstrate that complete (010) or (00) orientation may be induced by both kinetic and "hydrophobic" effects.The former is achieved through inhibition of nucleation and growth of the say (010) oriented crystals , by (S) amino acids in solution, while the latter is due to induction of (00) orientation by (S) hydrophobic amino acids.By symmetry the enantiomers induce opposite orientation.The two effects are investigated separately, and possible mechanisms are proposed.Combimation of the two effects, which operate in the same direction, allows total orientation of glycin crystals and thus triggering of amplification starting with a solution containing leucine with an enantiomeric excess as low as 6percent.The relevance of such a mechanism to other systems and to nucleation in general is discussed.
Characterization of d-amino acid aminotransferase from Lactobacillus salivarius
Kobayashi, Jyumpei,Shimizu, Yasuhiro,Mutaguchi, Yuta,Doi, Katsumi,Ohshima, Toshihisa
, p. 15 - 22 (2013)
We searched a UniProt database of lactic acid bacteria in an effort to identify d-amino acid metabolizing enzymes other than alanine racemase. We found a d-amino acid aminotransferase (d-AAT) homologous gene (UniProt ID: Q1WRM6) in the genome of Lactobacillus salivarius. The gene was then expressed in Escherichia coli, and its product exhibited transaminase activity between d-alanine and α-ketoglutarate. This is the first characterization of a d-AAT from a lactic acid bacterium. L. salivarius d-AAT is a homodimer that uses pyridoxal-5′-phosphate (PLP) as a cofactor; it contains 0.91 molecules of PLP per subunit. Maximum activity was seen at a temperature of 60 °C and a pH of 6.0. However, the enzyme lost no activity when incubated for 30 min at 30 °C and pH 5.5 to 9.5, and retained half its activity when incubated at pH 4.5 or 11.0 under the same conditions. Double reciprocal plots of the initial velocity and d-alanine concentrations in the presence of several fixed concentrations of α-ketoglutarate gave a series of parallel lines, which is consistent with a Ping-Pong mechanism. The Km values for d-alanine and α-ketoglutarate were 1.05 and 3.78 mM, respectively. With this enzyme, d-allo-isoleucine exhibited greater relative activity than d-alanine as the amino donor, while α-ketobutylate, glyoxylate and indole-3-pyruvate were all more preferable amino acceptors than α-ketoglutarate. The substrate specificity of L. salivarius d-AAT thus differs greatly from those of the other d-AATs so far reported.
Asymmetric Transamination of α-Keto Acids Catalyzed by Chiral Pyridoxamines
Lan, Xiaoyu,Tao, Chuangan,Liu, Xuliang,Zhang, Aina,Zhao, Baoguo
supporting information, p. 3658 - 3661 (2016/08/16)
A new type of novel chiral pyridoxamines 3a-g containing a side chain has been developed. The pyridoxamines displayed catalytic activity and promising enantioselectivity in biomimetic asymmetric transamination of α-keto acids, to give various α-amino acids in 47-90% yields with up to 87% ee's under very mild conditions. An interesting effect of the side chain on enantioselectivity was observed in the reaction.
