Investigation of how gate residues in the main channel affect the catalytic activity of Scytalidium thermophilum catalase.
Acta Crystallogr D Struct Biol
; 80(Pt 2): 101-112, 2024 Feb 01.
Article
em En
| MEDLINE
| ID: mdl-38265876
ABSTRACT
Catalase is an antioxidant enzyme that breaks down hydrogen peroxide (H2O2) into molecular oxygen and water. In all monofunctional catalases the pathway that H2O2 takes to the catalytic centre is via the `main channel'. However, the structure of this channel differs in large-subunit and small-subunit catalases. In large-subunit catalases the channel is 15â
Å longer and consists of two distinct parts, including a hydrophobic lower region near the heme and a hydrophilic upper region where multiple H2O2 routes are possible. Conserved glutamic acid and threonine residues are located near the intersection of these two regions. Mutations of these two residues in the Scytalidium thermophilum catalase had no significant effect on catalase activity. However, the secondary phenol oxidase activity was markedly altered, with kcat and kcat/Km values that were significantly increased in the five variants E484A, E484I, T188D, T188I and T188F. These variants also showed a lower affinity for inhibitors of oxidase activity than the wild-type enzyme and a higher affinity for phenolic substrates. Oxidation of heme b to heme d did not occur in most of the studied variants. Structural changes in solvent-chain integrity and channel architecture were also observed. In summary, modification of the main-channel gate glutamic acid and threonine residues has a greater influence on the secondary activity of the catalase enzyme, and the oxidation of heme b to heme d is predominantly inhibited by their conversion to aliphatic and aromatic residues.
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Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Ácido Glutâmico
/
Peróxido de Hidrogênio
Idioma:
En
Revista:
Acta Crystallogr D Struct Biol
Ano de publicação:
2024
Tipo de documento:
Article
País de publicação:
EEUU
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ESTADOS UNIDOS
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ESTADOS UNIDOS DA AMERICA
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EUA
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UNITED STATES
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UNITED STATES OF AMERICA
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US
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USA