Some Amines as Inhibitors of Pea Diamine Oxidase

Abstract

The inhibition of pea diamine oxidase (DAO; EC 1.4.3.6) by some amines and chelating agents has been studied. Ethylenediamine (competitive, K_i = 5.2 mmol.1^-1), cis-1,2-diaminocyclohexane (noncompetitive, K_i = 2.9 mmol.1^-1) and trans- 1,2-diaminocyclohexane (competitive, K_i = 3.6 mmol.1^-1) are weak inhibitors whereas diethylenetriamine (noncompetitive, K_i = 7.2 /imol.1^-1), triethylenetetraamine (partial noncompetitive, K_i = 0.57 μmol.1^-1) are potent inhibitors. The chelating agents 1,10-phenanthroline (K_i = 0.031 mmol.1^-1), and 2,2′-bipyridyl (K_i = 0.058 mmol.1^-1) are noncompetitive inhibitors. The pH-inhibition profile for the inhibitors indicates that the protonated forms are the active species.

Key Words: :

• Pea diamine oxidase
• amines
• chelating agents
• inhibitors