Feb 8, 1996

A study of a series of recombinant fungal laccases and bilirubin oxidase that exhibit significant differences in redox potential, substrate specificity, and stability

Biochimica Et Biophysica Acta
F XuE I Solomon

Abstract

A series of fungal laccases (Polyporus pinsitus, Rhizoctonia solani, Myceliophthora thermophila, Scytalidium thermophilum) and one bilirubin oxidase (Myrothecium verrucaria) have been studied to determine their redox potential, specificity, and stability. Polyporus and Rhizoctonia laccases possess potentials near 0.7-0.8 V (vs. NHE), while other oxidases have potentials near 0.5 V. It is observed that higher redox potential correlates with higher activity. By EPR, no significant change in the geometry of type 1 copper (II) site is observed over this series. At the optimal pH, the two substrates studied, 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulfonic acid) and syringaldazine, show Km values ranging form 10 to 120 and from 1 to 45 microM; and kcat values ranging from 50 to 16 000 and 200 to 3000 per min, respectively. The enzymes are more stable in the neutral-alkaline pH range. The thermal stability is in the order of bilirubin oxidase equivalent to Myceliophthora laccase equivalent to Scytalidium laccase > Polyporus laccase > Rhizoctonia laccase. Based on these results and the sequence alignments made against Zucchini ascorbate oxidase it is speculated that structural differences in the substrate-activation site (a 'blue', typ...Continue Reading

  • References12
  • Citations146

References

  • References12
  • Citations146

Citations

Mentioned in this Paper

Syringaldazine
Thermodynamics
Myceliophthora
Oxidoreductases Acting on CH-CH Group Donors
Enzymes, antithrombotic
Polyporus pinsitus
Proteins, Recombinant DNA
Filamentous fungus
Oxidase
Rhizoctonia

About this Paper

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