2Department of Biology M. C. A. Sciences, University of Camerino, 2 Via Camerini, 62032 Camerino (MC), Italy; fax: +39 (0737) 403290; E-mail: email@example.com
3Department of Chemical Sciences, University of Camerino, 1 Via S. Agostino, 62032 Camerino (MC), Italy; fax: 39 (0737) 402252; E-mail: firstname.lastname@example.org
* To whom correspondence should be addressed.
Received November 6, 2007; Revision received November 29, 2007
Dipeptidyl peptidase II (DPPII) from bovine kidney cortex and lung was purified to the electrophoretically homogeneous state. The molecular and catalytic characteristics of the enzyme were determined. It was revealed that DPPII preparations possess adenosine deaminase (ADA) activity at all purification steps. For the first time, the ADA-binding ability of DPPII has been shown similar to the well-known ADA-binding enzyme, DPPIV. The dissociation constant of the DPPII-ADA complex was estimated using a resonant mirror biosensor (80 nM), fluorescence polarization (60 nM), and differential spectroscopy (36 nM) techniques. The data demonstrate that DPPII can form a complex with ADA, but with one order of magnitude higher dissociation constant than that of DPPIV (7.8 nM).
KEY WORDS: dipeptidyl peptidase, adenosine deaminase, protein-protein interactions, fluorescence polarization, resonant mirror biosensor, differential spectrophotometry