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PDBsum entry 5kqh
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Oxidoreductase
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PDB id
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5kqh
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References listed in PDB file
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Key reference
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Title
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The catalase activity of catalase-Peroxidases is modulated by changes in the pka of the distal histidine.
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Authors
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M.Machuqueiro,
B.Victor,
J.Switala,
J.Villanueva,
C.Rovira,
I.Fita,
P.C.Loewen.
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Ref.
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Biochemistry, 2017,
56,
2271-2281.
[DOI no: ]
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PubMed id
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Abstract
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The unusual Met-Tyr-Trp adduct composed of cross-linked side chains along with
an associated mobile Arg is essential for catalase activity in
catalase-peroxidases. In addition, acidic residues in the entrance channel, in
particular an Asp and a Glu ∼7 and ∼15 Å, respectively, from the heme,
significantly enhance catalase activity. The mechanism by which these channel
carboxylates influence catalase activity is the focus of this work. Seventeen
new variants with fewer and additional acidic residues have been constructed and
characterized structurally and for enzymatic activity, revealing that their
effect on activity is roughly inversely proportional to their distance from the
heme and adduct, suggesting that the electrostatic potential of the heme cavity
may be affected. A discrete group of protonable residues are contained within a
15 Å sphere surrounding the heme iron, and a computational analysis reveals
that the pKa of the distal His112, alone, is modulated within the pH range of
catalase activity by the remote acidic residues in a pattern consistent with its
protonated form having a key role in the catalase reaction cycle. The
electrostatic potential also impacts the catalatic reaction through its
influence on the charged status of the Met-Tyr-Trp adduct.
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