- A new biocatalytic route to enantiopure N-carbamoyl amino acids by fast enzyme screening
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The enantioselective enzymatic deamidation of (rac)-N-carbamoyl amino acid amides (Cbm-AA-NH2) to enantiopure (L)-N-carbamoyl amino acids (Cbm-AA-OH) is described for the first time. Via fast screening methods of biocatalysts several proteases like Chirazyme P1, Chirazyme P2 and Subtilisin were identified, which give conversions of up to 47% and >98% ee. This conversion is most productive on aliphatic and primary amino acids.
- Trauthwein, Harald,May, Oliver,Dingerdissen, Uwe,Buchholz, Stefan,Drauz, Karlheinz
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- Microwave-assisted synthesis of N-monosubstituted urea derivatives
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An easy and rapid procedure for the preparation of N-monosubstituted ureas via reaction between potassium cyanate and a wide range of amines is described. The procedure was performed under microwave irradiation using water as solvent. This methodology is particularly attractive since it provides ureas in high yield and purity. Georg Thieme Verlag Stuttgart · New York.
- De Luca, Lidia,Porcheddu, Andrea,Giacomelli, Giampaolo,Murgia, Irene
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scheme or table
p. 2439 - 2442
(2010/11/18)
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- Rapid and efficient microwave-assisted synthesis of N-carbamoyl-L-amino acids
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A rapid and efficient method for the synthesis of N-carbamoyl-L-amino acids is reported. The procedure, involving the reaction between urea and α-amino acids sodium salts, was performed under microwave conditions using an unmodified domestic microwave oven. A careful study of the operative conditions indicated proline (1d) as the less reactive substrate and phenylglycine (1e) as the more reactive one among all the α-amino acids tested. Substitution of urea with potassium cyanate produced a low conversion into the corresponding N-carbamoyl derivative, and a possible explanation of this result is reported. Copyright Taylor & Francis Group, LLC.
- Verardo, Giancarlo,Geatti, Paola,Strazzolini, Paolo
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p. 1833 - 1844
(2008/02/02)
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- Mechanism of stereospecific conversion of DL-5-substituted hydantoins to the corresponding L-amino acids by Pseudomonas sp. strain NS671
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The mechanism of stereospecific conversion of DBL-5-substituted hydantoins to the corresponding L-amino acids by Pseudomonas sp. strain NS671 was studied. The results indicated that the hydantoinase catalyzed the hydrolysis reaction of both D- and L-5-(2-methylthioethyl)hydantoin, and that the hydrolysis of the L-enantiomer proceeded preferentially compared with that of the D-enantiomer. On the basis of these findings, the mechanism was speculated to be as follows: DBL-5-substituted hydantoins are converted exclusively to the L-forms of the corresponding N-carbamyl-amino acids by the hydantoinase in combination with hydantoin racemase. The N-carbamyl-L-amino acids are then converted to L-amino acids by N-carbamyl-L-amino acid amidohydrolase.
- Ishikawa, Takahiro,Watabe, Ken,Mukohara, Yukuo,Nakamura, Hiroaki
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p. 185 - 187
(2007/10/03)
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- Microbial Conversion of DL-5-Substituted Hydantoins to the Corresponding L-Amino Acids by Pseudomonas sp. Strain NS671
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A bacterial strain, NS671, which converts DL-5-(2-methylthioethyl)hydantoin stereospecifically to L-methionine, was isolated from soil and was classified into the genus Pseudomonas.With growing cells of Pseudomonas sp. strain NS671, DL-5-(2-methylthioethyl)hydantoin was effectively converted to L-methionine.Under adequate conditions, 34 g of L-methionine per liter was produced with a molar yield of 93percent from DL-5-(2-methylthioethyl)hydantoin added succesively.In addition to L-methionine, other amino acids such as L-valine, L-leucine, L-isoleucine, and L-phenylalanine were also produced from the corresponding 5-substituted hydantoins, but these L-amino acids produced were partially consumed by strain NS671.The hydantoinase, by which 5-substituted hydantoin rings are opened, was ATP-dependent.The N-carbamyl-amino acid amidohydrolase was found to be strictly L-specific, and its activity was inhibited by high concentration of ATP.
- Ishikawa, Takahiro,Watabe, Ken,Mukohara, Yukuo,Kobayashi, Shinobu,Nakamura, Hiroaki
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p. 982 - 986
(2007/10/02)
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- Mechanism of Stereospecific Production of L-Amino Acids from the Corresponding 5-Substituted Hydantoins by Bacillus brevis
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The mechanism of stereospecific production of L-amino acids from the corresponding 5-substituted hydantoins by Bacillus brevis AJ-12299 was studied.The enzymes involved in the reaction were partially purified by DEAE-Toyopearl 650M column chromatography and their properties were investigated.The conversion of DL-5-substituted hydantoins to the corresponding L-amino acids consisted of the following two successive reactions.The first step was the ring-opening hydrolysis to N-carbamoyl amino acids catalyzed by an ATP dependent L-5-substituted hydantoin hydrolase.This reaction was stereospecific and the N-carbamoyl amino acid produced was exclusively the L-form.N-Carbamoyl-L-amino acid was also produced from the D-form of 5-substituted hydantoin, which suggests that spontaneous racemization occurred in the reaction mixture.In the second step, N-carbamoyl-L-amino acid was hydrolyzed to L-amino acid by an N-carbamoyl-L-amino acid hydrolase, which was also an L-specific enzyme.The ATP dependency of the L-5-substituted hydantoin hydrolase was supposed to be the limiting factor in the production of L-amino acids from the corresponding 5-substituted hydantoins by this bacterium.
- Yamashiro, Akihiro,Kubota, Koji,Yokozeki, Kenzo
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p. 2857 - 2864
(2007/10/02)
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