Flexibility of the coordination geometry around the cupric ions in Cu(II)-rat dipeptidyl peptidase III is important for the expression of enzyme activity.

Junzo Hirose, Toshiyuki Hata, Chie Kawaoka, Tomohiro Ikeura, Suguru Kitahara, Kozue Horii, Hisao Tomida, Hiroyuki Iwamoto, Yukio Ono, Kayoko M Fukasawa

Index: Arch. Biochem. Biophys. 525(1) , 71-81, (2012)

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Abstract

Dipeptidyl peptidase III (DPP III), the zinc peptidase, has a unique helix portion in the metal-binding motif (HELLGH). The enzyme activity of the cupric derivative of rat DPP III (Cu(II)-rat DPP III) for Lys-Ala-β-NA is about 30% of that of the wild-type enzyme. On the other hand, the enzyme activity of Cu(II)-rat del-DPP III, in which Leu453 is deleted from the metal-binding motif, possesses only 1-2% of the enzyme activity of rat del-DPP III. The EPR spectra of Cu(II)-rat DPP III in the presence of various concentrations of the substrate, Lys-Ala-β-NA, changed dramatically, showing formation of the enzyme-metal-substrate complex. The EPR spectra of Cu(II)-rat del-DPP III did not change in the presence of excess Lys-Ala-β-NA. The deletion of Leu453 from the HELLGH motif of rat DPP III leads to a complete loss of flexibility in the ligand geometry around the cupric ions. Under the formation of the enzyme-metal-substrate complex, Glu451 of Cu(II)-rat DPP III is sufficiently able to approach the water molecule via a very different orientation from that of the resting state; however, Glu451 of Cu(II)-rat del-DPP III is not able to access the water molecule.Copyright © 2012 Elsevier Inc. All rights reserved.