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Characterization of the active site of group B streptococcal hyaluronan lyase
Author(s) -
Pritchard David G.,
Trent John O.,
Zhang Pei,
Egan Marianne L.,
Baker John R.
Publication year - 2000
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/(sici)1097-0134(20000701)40:1<126::aid-prot140>3.0.co;2-4
Subject(s) - lyase , active site , biochemistry , enzyme , asparagine , amino acid , site directed mutagenesis , chemistry , stereochemistry , mutant , gene
Hyaluronan lyase is secreted by most strains of the human pathogen, group B streptococcus. Site‐directed mutagenesis of the enzyme identified three amino acid residues important for enzyme activity, H479, Y488, and R542. These three residues are in close proximity in the putative active site of a homology model of group B streptococcal hyaluronan lyase. The homology model was based on the crystal structure of another related glycosaminoglycan lyase, chondroitin AC lyase, which exhibits different substrate specificity. Two asparagine residues in the active site groove, N429 and N660, were also found to be essential for enzyme activity. In addition, conversion of two adjacent tryptophan residues in the groove to alanines abolished activity. All amino acids found to be essential in GBS hyaluronan lyase are conserved in both enzymes. However, several amino acids in the active site groove of the two enzymes are not conserved. In the 18 cases in which one of these amino acids in GBS hyaluronan lyase was replaced with its corresponding amino acid in chondroitin AC lyase, no major loss of activity or change in substrate specificity was observed. Proteins 2000;40:126–134. © 2000 Wiley‐Liss, Inc.