Divalent metal activation of a GH43 β-xylosidase

Charles C. Lee*, Jay D. Braker, Arabela A Grigorescu, Kurt Wagschal, Douglas B. Jordan

*Corresponding author for this work

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

Depolymerization of xylan, a major fraction of lignocellulosic biomass, releases xylose which can be converted into transportation fuels and chemical feedstocks. A requisite enzyme for the breakdown of xylan is β-xylosidase. A gene encoding the 324-amino acid β-xylosidase, RS223-BX, was cloned from an anaerobic mixed microbial culture. This glycoside hydrolase belongs to family 43. Unlike other GH43 enzymes, RS223-BX can be strongly activated by exogenously supplied Ca2+, Co2+, Fe2+, Mg2+, Mn2+ and Ni2+ (e.g., 28-fold by Mg2+) and it is inhibited by Cu2+ or Zn2+. Sedimentation equilibrium centrifugation experiments indicated that the divalent metal cations mediate multimerization of the enzyme from a dimeric to a tetrameric state, which have equal catalytic activity on an active-site basis. Compared to the determined active sites of other GH43 β-xylosidases, the predicted active site of RS223-BX contains two additional amino acids with carboxylated side chains that provide potential sites for divalent metal cations to reside. Thus, the divalent metal cations likely occupy the active site and participate in the catalytic mechanism. RS223-BX accepts as substrate xylobiose, arabinobiose, 4-nitrophenyl-β-d-xylopyranoside, and 4-nitrophenyl-α-l-arabinofuranoside. Additionally, the enzyme has good pH and temperature stabilities and a large Ki for d-glucose (1.3M), favorable properties for performance in saccharification reactors.

Original languageEnglish (US)
Pages (from-to)84-90
Number of pages7
JournalEnzyme and Microbial Technology
Volume52
Issue number2
DOIs
StatePublished - Feb 5 2013

Fingerprint

Xylosidases
Catalytic Domain
Divalent Cations
Enzymes
Metals
Chemical activation
Cations
Xylans
Positive ions
Amino acids
Amino Acids
Saccharification
Depolymerization
Gene encoding
Xylose
Centrifugation
Glycoside Hydrolases
Sedimentation
Biomass
Feedstocks

Keywords

  • β-Xylosidase
  • Divalent cation
  • Hemicellulose
  • Multimerization

ASJC Scopus subject areas

  • Biotechnology
  • Biochemistry
  • Applied Microbiology and Biotechnology

Cite this

Lee, Charles C. ; Braker, Jay D. ; Grigorescu, Arabela A ; Wagschal, Kurt ; Jordan, Douglas B. / Divalent metal activation of a GH43 β-xylosidase. In: Enzyme and Microbial Technology. 2013 ; Vol. 52, No. 2. pp. 84-90.
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Divalent metal activation of a GH43 β-xylosidase. / Lee, Charles C.; Braker, Jay D.; Grigorescu, Arabela A; Wagschal, Kurt; Jordan, Douglas B.

In: Enzyme and Microbial Technology, Vol. 52, No. 2, 05.02.2013, p. 84-90.

Research output: Contribution to journalArticle

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T1 - Divalent metal activation of a GH43 β-xylosidase

AU - Lee, Charles C.

AU - Braker, Jay D.

AU - Grigorescu, Arabela A

AU - Wagschal, Kurt

AU - Jordan, Douglas B.

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N2 - Depolymerization of xylan, a major fraction of lignocellulosic biomass, releases xylose which can be converted into transportation fuels and chemical feedstocks. A requisite enzyme for the breakdown of xylan is β-xylosidase. A gene encoding the 324-amino acid β-xylosidase, RS223-BX, was cloned from an anaerobic mixed microbial culture. This glycoside hydrolase belongs to family 43. Unlike other GH43 enzymes, RS223-BX can be strongly activated by exogenously supplied Ca2+, Co2+, Fe2+, Mg2+, Mn2+ and Ni2+ (e.g., 28-fold by Mg2+) and it is inhibited by Cu2+ or Zn2+. Sedimentation equilibrium centrifugation experiments indicated that the divalent metal cations mediate multimerization of the enzyme from a dimeric to a tetrameric state, which have equal catalytic activity on an active-site basis. Compared to the determined active sites of other GH43 β-xylosidases, the predicted active site of RS223-BX contains two additional amino acids with carboxylated side chains that provide potential sites for divalent metal cations to reside. Thus, the divalent metal cations likely occupy the active site and participate in the catalytic mechanism. RS223-BX accepts as substrate xylobiose, arabinobiose, 4-nitrophenyl-β-d-xylopyranoside, and 4-nitrophenyl-α-l-arabinofuranoside. Additionally, the enzyme has good pH and temperature stabilities and a large Ki for d-glucose (1.3M), favorable properties for performance in saccharification reactors.

AB - Depolymerization of xylan, a major fraction of lignocellulosic biomass, releases xylose which can be converted into transportation fuels and chemical feedstocks. A requisite enzyme for the breakdown of xylan is β-xylosidase. A gene encoding the 324-amino acid β-xylosidase, RS223-BX, was cloned from an anaerobic mixed microbial culture. This glycoside hydrolase belongs to family 43. Unlike other GH43 enzymes, RS223-BX can be strongly activated by exogenously supplied Ca2+, Co2+, Fe2+, Mg2+, Mn2+ and Ni2+ (e.g., 28-fold by Mg2+) and it is inhibited by Cu2+ or Zn2+. Sedimentation equilibrium centrifugation experiments indicated that the divalent metal cations mediate multimerization of the enzyme from a dimeric to a tetrameric state, which have equal catalytic activity on an active-site basis. Compared to the determined active sites of other GH43 β-xylosidases, the predicted active site of RS223-BX contains two additional amino acids with carboxylated side chains that provide potential sites for divalent metal cations to reside. Thus, the divalent metal cations likely occupy the active site and participate in the catalytic mechanism. RS223-BX accepts as substrate xylobiose, arabinobiose, 4-nitrophenyl-β-d-xylopyranoside, and 4-nitrophenyl-α-l-arabinofuranoside. Additionally, the enzyme has good pH and temperature stabilities and a large Ki for d-glucose (1.3M), favorable properties for performance in saccharification reactors.

KW - β-Xylosidase

KW - Divalent cation

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KW - Multimerization

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