Chi-Yue Wu

Specific Peptide-Bond Cleavage by Microwave Irradiation in Weak Acid Solution

A rapid and selective peptide-bond cleavage in weak acid, induced by microwave irradiation, has been developed. The specific cleavage sites of peptide bonds located only at the carboxyl-and amino-terminal ends of aspartyl residues along the peptide chain. A systematic study including the time course for the cleavage of various aspartyl-containing peptides, the effect of the acidity of the reaction solution on the completeness of peptide-bond cleavage, and the relationship between the power of microwave irradiation and the reaction time of cleavage are studied.

Kinetic analysis of duck ε-crystallin with l-lactate dehydrogenase activity: Determination of kinetic constants and comparison of substrate specificity

A systematic analysis of the kinetic properties of duck lens epsilon-crystallin with lactate dehydrogenase [LDH, (E.C. 1.1.1.27)] activity was carried out by employing some 19 different alpha-keto acids as substrates for this NADH-dependent LDH-catalyzed reaction. The steady-state Michaelis and catalytic constants (Km, kcat) were determined for a broad range of organic compounds. The results provide important insights regarding the binding and affinity of substrates to active sites of this enzyme crystallin and indicate a great potential for the application of the stable epsilon-crystallin as a catalyst to the synthesis of some important chiral alpha-hydroxyacids in a convenient and efficient way. It is also demonstrated for the first time that in addition to the enzymatic activity of lactate dehydrogenase, duck epsilon-crystallin also possesses the enzymatic activity of malate dehydrogenase.

Facile synthesis of chiral 2-hydroxy acids catalyzed by a stable duck ε-crystallin with endogenous l-lactate dehydrogenase activity

Duck ε‐crystallin, an abundant structural protein in lenses of some avian species, was shown to possess a genuine and stable l‐lactate dehydrogenase (l‐LDH, EC 1.1.1.27) activity suitable for the application to enzyme technology as a catalyst for the synthesis of chiral α‐hydroxy acids. Two pharmaceutically important intermediates, 2‐hydroxy acids (S)‐2‐hydroxybutanoic acid (S)‐2‐hydroxypentanoic acid) have been synthesized in high yields and Optical purity utilizing an in situ NADH regeneration system of duck ε‐crystallin coupled with formate/formate dehydrogenase. This enzyme system is also shown to offer some advantages over the conventional l‐LDH sources from several mammalian species.

Engineering of cyclic peptides with novel inhibiting properties to differentiate two serine proteases, chymotrypsin and subtilisin Carlsberg

Based on the crystal structure of the inhibitory loop of barley chymotrypsin inhibitor II (CI-II), two cyclic peptides, I- 1 and I- 2, were designed and synthesized chemically. I- 1 is a noncompetitive inhibitor for chymotrypsin and an uncompetitive inhibitor for subtilisin Carlsberg. I- 2 exhibited competitive inhibition of both chymotrypsin and subtilisin Carlsberg. The results indicate that the hydrophobic region of the inhibitory loop of CI-II plays an important role for CI-II to bind to the active sites of proteases. Based on the crystal structure of the inhibitory loop of barley chymotrypsin inhibitor II (CI-II), two cyclic peptides, I- 1 and I- 2, were designed and synthesized chemically. I- 1 is a noncompetitive inhibitor for chymotrypsin and an uncompetitive inhibitor for subtilisin Carlsberg. I- 2 exhibited competitive inhibition of both chymotrypsin and subtilisin Carlsberg. The results indicate that the hydrophobic region of the inhibitory loop of CI-II plays an important role for CI-II to bind to the active sites of proteases.