Structural and catalytic properties of the four phenylalanine ammonia-lyase isoenzymes from parsley (Petroselinum crispum Nym.)

Eur J Biochem. 1994 Oct 1;225(1):491-9. doi: 10.1111/j.1432-1033.1994.00491.x.


Near-full-length cDNAs for the four phenylalanine ammonia-lyase (PAL) isoenzymes in parsley (Petroselium crispum Nym.) were cloned and the complete amino acid sequences deduced. Fusion proteins with glutathione S-transferase were expressed in Escherichia coli, purified and cleaved. All of the resulting phenylalanine ammonia-lyase proteins, as well as the fusion proteins, were catalytically active. The turnover number of one selected isoenzyme, PAL-1, was estimated to be around 22 s-1 for each active site. In contrast to a certain degree of differential expression in various parts of parsley plants, the four phenylalanine ammonia-lyase isoenzymes exhibited very similar apparent Km values for L-phenylalanine (15-24.5 microM) as well as identical temperature (58 degrees C) and pH (8.5) optima. All of them were competitively inhibited by (E)-cinnamate with similar efficiency (Ki values: 9.1-21.5 microM), lacked cooperative behaviour, and accepted L-tyrosine as a substrate with low affinity (Km values: 2.6-7.8 mM). These results suggest that the occurrence of multiple gene copies has a function other than encoding isoenzymes with different enzyme kinetic properties.

Publication types

  • Comparative Study

MeSH terms

  • Amino Acid Sequence
  • Binding Sites
  • Consensus Sequence
  • DNA, Complementary
  • Electrophoresis, Polyacrylamide Gel
  • Isoenzymes / chemistry*
  • Isoenzymes / isolation & purification
  • Isoenzymes / metabolism*
  • Kinetics
  • Magnoliopsida / enzymology*
  • Molecular Sequence Data
  • Phenylalanine Ammonia-Lyase / chemistry*
  • Phenylalanine Ammonia-Lyase / isolation & purification
  • Phenylalanine Ammonia-Lyase / metabolism*
  • Recombinant Fusion Proteins / isolation & purification
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / isolation & purification
  • Recombinant Proteins / metabolism
  • Sequence Homology, Amino Acid


  • DNA, Complementary
  • Isoenzymes
  • Recombinant Fusion Proteins
  • Recombinant Proteins
  • Phenylalanine Ammonia-Lyase

Associated data

  • GENBANK/M84466
  • GENBANK/X81158
  • GENBANK/X81159