Altering the Properties of Laccases from <i>Ensifer meliloti</i> (<i>Sinorhizobium meliloti</i>) and <i>Cerrena unicolor</i> by Chemical Modifications of Proteins

Due to their catalytic performance, laccases constitute one of the most promising groups of enzymes for potential applications in modern biotechnology. In this study, we aimed to chemically modify <i>Ensifer meliloti</i> (<i>Sinorhizobium meliloti</i>) and <i>Cerrena un...

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Main Authors: Anna Pawlik, Radosław Drozd, Grzegorz Janusz
Format: Article
Language:English
Published: MDPI AG 2025-04-01
Series:Biomolecules
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Online Access:https://www.mdpi.com/2218-273X/15/4/531
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author Anna Pawlik
Radosław Drozd
Grzegorz Janusz
author_facet Anna Pawlik
Radosław Drozd
Grzegorz Janusz
author_sort Anna Pawlik
collection DOAJ
description Due to their catalytic performance, laccases constitute one of the most promising groups of enzymes for potential applications in modern biotechnology. In this study, we aimed to chemically modify <i>Ensifer meliloti</i> (<i>Sinorhizobium meliloti</i>) and <i>Cerrena unicolor</i> laccase and comparatively characterize the structures of both enzymes. The most characteristic feature was the spatial localization of lysine residues, predominantly positioned distal to the active site region for both compared enzymes. The solvent-accessible surface area (SASA) analysis showed that bacterial laccase was characterized by a larger hydrophobic SASA than the fungal enzyme. The pK<sub>a</sub> prediction identified only one Lys in the <i>E. meliloti</i> laccase structure susceptible to modification. Modifications were achieved by using mono- and bifunctional crosslinking agents, and glycosylations were also performed. The degree of protein modification ranged from 0% for glucose- and galactose-modified <i>E. meliloti</i> laccase and citraconic anhydride-modified (CA) <i>C. unicolor</i> laccase to 62.94% for the palmitic acid N-hydroxysuccinimide ester-modified <i>E. meliloti</i> enzyme. The stability of covalently modified laccases over a wide pH and temperature ranges and in the presence of inhibitors was investigated. Protein modifications with polymeric sucrose (PS) and ethylene glycol bis-(succinimidyl succinate) (EGNHS) significantly increased the activity of the bacterial and fungal laccases by 15 and 19%, respectively. Although pH optima remained relatively unchanged by modifications, certain variants, especially CA-modified bacterial protein and EGNHS-modified <i>C. unicolor</i> enzyme, exhibited improved stability at near-neutral pH (6–7). Modification of the bacterial enzyme with glutaraldehyde-carbodiimide (GA-CDI-ver) and of the fungal enzyme with CA was the most effective in improving its thermal stability. Chemical modifications using GA, CDI, GA-CDI, and PS allowed <i>E. meliloti</i> L 3.8 laccase to retain full activity in the presence of 5 mM NaI, whereas CA-, PS-, and EGNHS-modified <i>C. unicolor</i> variants retained their activity even at elevated NaCl concentrations. The results clearly demonstrate that the outcome of chemical modifications is closely linked to enzyme-specific structural features and that selecting an appropriate modification strategy is critical to achieving the desired effect.
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spelling doaj-art-d8393724e0f2497f831ea85f9e46d3fd2025-08-20T03:14:17ZengMDPI AGBiomolecules2218-273X2025-04-0115453110.3390/biom15040531Altering the Properties of Laccases from <i>Ensifer meliloti</i> (<i>Sinorhizobium meliloti</i>) and <i>Cerrena unicolor</i> by Chemical Modifications of ProteinsAnna Pawlik0Radosław Drozd1Grzegorz Janusz2Department of Biochemistry and Biotechnology, Institute of Biological Sciences, Maria Curie-Sklodowska University, Akademicka 19 St., 20-033 Lublin, PolandDepartment of Microbiology and Biotechnology, Faculty of Biotechnology and Animal Husbandry, West Pomeranian University of Technology in Szczecin, 45 Piastow Avenue, 71-311 Szczecin, PolandDepartment of Biochemistry and Biotechnology, Institute of Biological Sciences, Maria Curie-Sklodowska University, Akademicka 19 St., 20-033 Lublin, PolandDue to their catalytic performance, laccases constitute one of the most promising groups of enzymes for potential applications in modern biotechnology. In this study, we aimed to chemically modify <i>Ensifer meliloti</i> (<i>Sinorhizobium meliloti</i>) and <i>Cerrena unicolor</i> laccase and comparatively characterize the structures of both enzymes. The most characteristic feature was the spatial localization of lysine residues, predominantly positioned distal to the active site region for both compared enzymes. The solvent-accessible surface area (SASA) analysis showed that bacterial laccase was characterized by a larger hydrophobic SASA than the fungal enzyme. The pK<sub>a</sub> prediction identified only one Lys in the <i>E. meliloti</i> laccase structure susceptible to modification. Modifications were achieved by using mono- and bifunctional crosslinking agents, and glycosylations were also performed. The degree of protein modification ranged from 0% for glucose- and galactose-modified <i>E. meliloti</i> laccase and citraconic anhydride-modified (CA) <i>C. unicolor</i> laccase to 62.94% for the palmitic acid N-hydroxysuccinimide ester-modified <i>E. meliloti</i> enzyme. The stability of covalently modified laccases over a wide pH and temperature ranges and in the presence of inhibitors was investigated. Protein modifications with polymeric sucrose (PS) and ethylene glycol bis-(succinimidyl succinate) (EGNHS) significantly increased the activity of the bacterial and fungal laccases by 15 and 19%, respectively. Although pH optima remained relatively unchanged by modifications, certain variants, especially CA-modified bacterial protein and EGNHS-modified <i>C. unicolor</i> enzyme, exhibited improved stability at near-neutral pH (6–7). Modification of the bacterial enzyme with glutaraldehyde-carbodiimide (GA-CDI-ver) and of the fungal enzyme with CA was the most effective in improving its thermal stability. Chemical modifications using GA, CDI, GA-CDI, and PS allowed <i>E. meliloti</i> L 3.8 laccase to retain full activity in the presence of 5 mM NaI, whereas CA-, PS-, and EGNHS-modified <i>C. unicolor</i> variants retained their activity even at elevated NaCl concentrations. The results clearly demonstrate that the outcome of chemical modifications is closely linked to enzyme-specific structural features and that selecting an appropriate modification strategy is critical to achieving the desired effect.https://www.mdpi.com/2218-273X/15/4/531laccase<i>Cerrena unicolor</i><i>Ensifer meliloti</i><i>Sinorhizobium meliloti</i>chemical modificationthermostability
spellingShingle Anna Pawlik
Radosław Drozd
Grzegorz Janusz
Altering the Properties of Laccases from <i>Ensifer meliloti</i> (<i>Sinorhizobium meliloti</i>) and <i>Cerrena unicolor</i> by Chemical Modifications of Proteins
Biomolecules
laccase
<i>Cerrena unicolor</i>
<i>Ensifer meliloti</i>
<i>Sinorhizobium meliloti</i>
chemical modification
thermostability
title Altering the Properties of Laccases from <i>Ensifer meliloti</i> (<i>Sinorhizobium meliloti</i>) and <i>Cerrena unicolor</i> by Chemical Modifications of Proteins
title_full Altering the Properties of Laccases from <i>Ensifer meliloti</i> (<i>Sinorhizobium meliloti</i>) and <i>Cerrena unicolor</i> by Chemical Modifications of Proteins
title_fullStr Altering the Properties of Laccases from <i>Ensifer meliloti</i> (<i>Sinorhizobium meliloti</i>) and <i>Cerrena unicolor</i> by Chemical Modifications of Proteins
title_full_unstemmed Altering the Properties of Laccases from <i>Ensifer meliloti</i> (<i>Sinorhizobium meliloti</i>) and <i>Cerrena unicolor</i> by Chemical Modifications of Proteins
title_short Altering the Properties of Laccases from <i>Ensifer meliloti</i> (<i>Sinorhizobium meliloti</i>) and <i>Cerrena unicolor</i> by Chemical Modifications of Proteins
title_sort altering the properties of laccases from i ensifer meliloti i i sinorhizobium meliloti i and i cerrena unicolor i by chemical modifications of proteins
topic laccase
<i>Cerrena unicolor</i>
<i>Ensifer meliloti</i>
<i>Sinorhizobium meliloti</i>
chemical modification
thermostability
url https://www.mdpi.com/2218-273X/15/4/531
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AT radosławdrozd alteringthepropertiesoflaccasesfromiensifermelilotiiisinorhizobiummelilotiiandicerrenaunicoloribychemicalmodificationsofproteins
AT grzegorzjanusz alteringthepropertiesoflaccasesfromiensifermelilotiiisinorhizobiummelilotiiandicerrenaunicoloribychemicalmodificationsofproteins