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Structural insights into the loss of catalytic competence in pectate lyase activity at low pH
Author(s) -
Ali Salyha,
Søndergaard Chresten R.,
Teixeira Susana,
Pickersgill Richard W.
Publication year - 2015
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2015.09.014
Subject(s) - pectate lyase , chemistry , lyase , protonation , catalysis , enzyme , carboxylate , active site , arginine , stereochemistry , residue (chemistry) , biochemistry , cleavage (geology) , organic chemistry , ion , pectinase , amino acid , biology , paleontology , fracture (geology)
Pectate lyase, a family 1 polysaccharide lyase, catalyses cleavage of the α‐1,4 linkage of the polysaccharide homogalacturonan via an anti β‐elimination reaction. In the Michaelis complex two calcium ions bind between the C6 carboxylate of the d ‐galacturonate residue and enzyme aspartates at the active centre (+1 subsite), they withdraw electrons acidifying the C5 proton facilitating its abstraction by the catalytic arginine. Here we show that activity is lost at low pH because protonation of aspartates results in the loss of the two catalytic calcium‐ions causing a profound failure to correctly organise the Michaelis complex.