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Journal Article 
A mutant leucine aminopeptidase from Streptomyces cinnamoneus with enhanced L: -aspartyl L: -amino acid methyl ester synthetic activity 
Arima, J; Kono, M; Kita, M; Mori, N 
In Press 
Biotechnology Letters
ISSN: 0141-5492
EISSN: 1573-6776 
L: -Aspartyl L: -amino acid methyl ester was synthesized using a mutant of a thermostable leucine aminopeptidase from Streptomyces cinnamoneus, D198 K SSAP, obtained in previously. A peptide of high-intensity sweetener, L: -aspartyl-L: -phenylalanine methyl ester, was selected as a model for demonstrating the synthesis of L: -aspartyl L: -amino acid methyl ester. The hydrolytic activities of D198 K SSAP toward L: -aspartyl-L: -phenylalanine and its methyl ester were, respectively, 74-fold and fourfold higher than those of wild type. Similarly, the initial rate of the enzyme for L: -aspartyl-L: -phenylalanine methyl ester synthesis was over fivefold higher than that of wild-type SSAP in 90% methanol (v/v) in a one-pot reaction. Furthermore, other L: -aspartyl L: -amino acid methyl esters were synthesized efficiently using D198 K SSAP. Results show that the substitution of Asp198 of SSAP with Lys is effective for synthesizing L: -aspartyl L: -amino acid methyl ester. 
Aminopeptidase; L-aspartyl-L-phenylalanine methyl ester; Peptide bond formation; Reverse reaction 
• Methanol (Non-Cancer)
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