Kinetic analysis of the inhibition of phenylalanine ammonia-lyase by 2-aminoindan-2-phosphonic acid and other phenylalanine analogues

The conformationally restricted phenylalanine analogue 2-aminoindan-2-phosphonic acid (AIP) inhibits phenylalanine ammonialyase (PAL) competitively in a time-dependent manner. This phenomenon was investigated in more detail with the heterologously expressed, highly purified homotetrameric PAL-1 isozyme from parsley. The kinetic analysis revealed that the enzyme-inhibitor complex is formed in a single "slow" step with an association rate of k(2) = 2.6 +/- 0.04 10(4) M-1 s(-1). The inhibition is reversible with a dissociation rate of k(-2) = 1.8 +/- 0.04 10(-4) s(-1) I and an equilibrium constant of K-i = 7 +/- 2 nM. The previously described PAL inhibitor (S)-2-aminooxy-3-phenylpropanoic acid [(S)-AOPP] was also found to be a slow-binding inhibitor of PAL-1. The carboxyl analogue of AIP, 2-aminoindan-2-carboxylic acid, served as a substrate of PAL-1 and was converted to indene-2-carboxylic acid. (C) 2003 Elsevier Science Ltd. All rights reserved.