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KMID : 0545119960060040250
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Journal of Microbiology and Biotechnology
1996 Volume.6 No. 4 p.250 ~ p.254
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The Slow and Tight Binding of MR-387A to Aminopeptidase N
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CHUNG, MYUNG-CHUL
CHUN, HYO-KON/LEE, HO-JAE/LEE, CHOONG-HWAN/KIM, SU-IL/KHO, YUNG-HEE
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Abstract
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MR-387A [(2S, 3R)-2-hydroxy-3-amino-4-phenylbutanotl-L-valyl-(2, 4-trans)-L-4-hydroxy-proline] reversibly inhibits aminopeptidase N (EC 3.4.11.2) in a process that is remarkable for its unusual degree of time dependence. The time required to inactivate the enzyme by 50% (t_1/2) for establishing steady-state levels of EI^* complex was approximately 5 minutes. This indicated that the inhibition is a slow-binding process. In dissociation experiments of EI^* complex, enzymic activity was regained slowly in a quadratic equation, indicating that the inhibition of aminopeptidase N by MR-387A is tight-binding and reversible. Thus, the binding of MR-387A by aminopeptidase N is slow and tight, with K_i (for initial collision complex, EI) and K_i^* (for final tightened complex, EI*) of 2.2×10^-8 M (from lineweaver-Burk plot) and 4.4×10^-10 M (from rate consistants), respectively. These data indicated that MR-387A and aminopeptidase N are bound approximately 200-fold more tightly in the final EI^* complex than in the initial collision EI complex.
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