title: Influence of reaction conditions on syntheses of sweetener precursors catalyzed by thermolysin in tert-amyl alcohol.
abstract: The activity of enzymes to form a peptide bond in organic solvent was greatly influenced by observed pH and water content. The precursors of two sweeteners, P-Asp-Xaa-OR (P=Z or For, Xaa-OR=Phe-OMe or Ala-OcHex), were synthesized by enzyme, and the reaction conditions were studied systematically. Z-Asp-OH was coupled with H-Phe-OMe or H-Ala-OcHex by thermolysin in tert-amyl alcohol. The best coupling results were obtained when the optimized observed pH was 8 or 9, and the water content was about 6% (V/V). The protecting group Z is better than For under the reaction conditions and H-Phe-OMe is a better nucleophile than H-Ala-OcHex. The expected optically pure peptides were obtained when the racemic amino acids were used as amino components in the starting materials. The physical constants of P-Asp-Xaa-OR synthesized by thermolysin are identical with those of peptides synthesized by chemical method.
authors.affiliation: Department of Chemistry, Peking University, Beijing, PR China.
authors.forename: G W
authors.initials: GW
authors.lastname: Xing
authors.forename: G L
authors.initials: GL
authors.lastname: Tian
authors.forename: Y H
authors.initials: YH
authors.lastname: Ye
mesh_terms: D002384:Catalysis; D000439:Pentanols / Q000737:chemistry; D013549:Sweetening Agents / Q000138:chemical synthesis* / Q000737:chemistry*; D013820:Thermolysin / Q000737:chemistry
chemical_list: D000439:Pentanols; D013549:Sweetening Agents; C032765:tert-amyl alcohol; D013820:Thermolysin