Dataset Information

Purification and Characterization of Phenylalanine Ammonia Lyase from Trichosporon cutaneum.

ABSTRACT: Trichosporon cutaneum phenylalanine ammonia lyase was selected as a model to investigate the dual substrate activity of this family of enzymes. Sequencing of the PAL gene identified an extensive intron region at the N-terminus. Five amino acid residues differing from a prior report were identified. Highest Phe?:?Tyr activities (1.6? ± 0.3?:?0.4 ± 0.1? ? mol/h?g wet weight) were induced by Tyr. The enzyme has a temperature optimum of 32°C and a pH optimum of 8-8.5 and shows no metal cofactor dependence. Michaelis-Menten kinetics (Phe, K m ??5.0? ± ?1.1?mM) and positive allostery (Tyr, K'??2.4? ± ?0.6?mM, Hill coefficient 1.9 ± 0.5) were observed. Anion exchange chromatography gave a purification fold of 50 with 20% yield. The His-Gln motif (substrate selectivity switch region) indicates the enzyme's ability to act on both substrates.

SUBMITTER: Goldson-Barnaby A

PROVIDER: S-EPMC3789393 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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Purification and Characterization of Phenylalanine Ammonia Lyase from Trichosporon cutaneum.

Goldson-Barnaby Andrea A Scaman Christine H CH

Enzyme research 20130912

Trichosporon cutaneum phenylalanine ammonia lyase was selected as a model to investigate the dual substrate activity of this family of enzymes. Sequencing of the PAL gene identified an extensive intron region at the N-terminus. Five amino acid residues differing from a prior report were identified. Highest Phe : Tyr activities (1.6 ± 0.3 : 0.4 ± 0.1 μ mol/h g wet weight) were induced by Tyr. The enzyme has a temperature optimum of 32°C and a pH optimum of 8-8.5 and shows no metal cofactor depe ...[more]

PMID: 24159382

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Project description:We have recently observed promising success in a mouse model for treating the metabolic disorder phenylketonuria with phenylalanine ammonia lyase (PAL) from Rhodosporidium toruloides and Anabaena variabilis. Both molecules, however, required further optimization in order to overcome problems with protease susceptibility, thermal stability, and aggregation. Previously, we optimized PAL from R. toruloides, and in this case we reduced aggregation of the A. variabilis PAL by mutating two surface cysteine residues (C503 and C565) to serines. Additionally, we report the structural and biochemical characterization of the A. variabilis PAL C503S/C565S double mutant and carefully compare this molecule with the R. toruloides engineered PAL molecule. Unlike previously published PAL structures, significant electron density is observed for the two active-site loops in the A. variabilis C503S/C565S double mutant, yielding a complete view of the active site. Docking studies and N-hydroxysuccinimide-biotin binding studies support a proposed mechanism in which the amino group of the phenylalanine substrate is attacked directly by the 4-methylidene-imidazole-5-one prosthetic group. We propose a helix-to-loop conformational switch in the helices flanking the inner active-site loop that regulates accessibility of the active site. Differences in loop stability among PAL homologs may explain the observed variation in enzyme efficiency, despite the highly conserved structure of the active site. A. variabilis C503S/C565S PAL is shown to be both more thermally stable and more resistant to proteolytic cleavage than R. toruloides PAL. Additional increases in thermal stability and protease resistance upon ligand binding may be due to enhanced interactions among the residues of the active site, possibly locking the active-site structure in place and stabilizing the tetramer. Examination of the A. variabilis C503S/C565S PAL structure, combined with analysis of its physical properties, provides a structural basis for further engineering of residues that could result in a better therapeutic molecule.

Dataset Information

Purification and Characterization of Phenylalanine Ammonia Lyase from Trichosporon cutaneum.

Publications

Purification and Characterization of Phenylalanine Ammonia Lyase from Trichosporon cutaneum.

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