Studies on the Catalytic Activity of Poly-α-amino Acids

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Abstract
By the interaction between the hydroxyl group of tyrosyl and the carboxyl group of glutamyl residue in poly (L-Tyr-L-Glu), copoly (L-Tyr, L-Glu, L-Ala) and copoly (L-Tyr, L-Glu, L-Pro), þ-nitrophenyl acetate was hydrolyzed catalytically, and the pH-activity relation showed a bell shape. Poly (L-Tyr-L-Glu), whose amino acid sequence is established, hydrolyzed NPA and showed an optimal condition similar to random copoly (L-Tyr, L-Glu) as shown previously. However, the apparent Vmax of poly (L-Tyr-L-Glu) (0.8×10−6 M/min) was about 1/10 of copoly (L-Tyr, L-Glu) (9.4× 10−6M/min). Although the data suggests that the primary arrangement of Tyr-Glu is not essential to the activity, the interaction between tyrosine and glutamic acid is essential to form an active site. The optimal condition of copoly (L-Tyr, L-Glu, L-Ala) was pH5.70 at 40°C and that of copoly (L-Tyr, L-Glu, L-Pro) was pH5.65 at 45°C. However, the optimal pH of the above two copolymers shifted about 0.4 pH units to a lower pH and the activities were a little higher inspited of the lower contents of tyrosine and glutamic acid than that of copoly (L-Tyr, L-Glu). The expected effect of the alanyl or prolyl residues, which might affect the secondary structure of molecule as a flexible factor to polypeptide, was not not so remarkable on the activity.

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