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Dependence of Catalytic Ability of Catalase‐peroxidase on Intersubunit Interactions
Author(s) -
Kudalkar Shalley Nidhish,
Goodwin Douglas C
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.715.10
Subject(s) - active site , peroxidase , heme , catalase , chemistry , cytochrome c peroxidase , hexacoordinate , enzyme , hydrogen peroxide , site directed mutagenesis , stereochemistry , mutagenesis , biochemistry , mutant , gene , organic chemistry , silicon
Catalase‐peroxidases (KatGs) serve as an ideal model to explore the role of distant protein structures and their interactions on enzyme active site structure and catalysis. KatG efficiently facilitates hydrogen peroxide decomposition by two pathways: catalase and peroxidase. However, the KatG active site is nearly identical to those of classical heme peroxidases (e.g., cytochrome c peroxidase), which have poor catalase activity. Obvious differences between these two groups of enzymes include a gene duplicated C‐terminal domain and two interhelical insertions unique to KatG. Deletion of any of these structures has deep impact on KatG active site environment and catalytic function (e.g., selective loss of catalase activity). To study the role of distant interactions between two of these KatG‐unique features, site‐directed and deletion mutagenesis were evaluated for changes in active site structure by various spectroscopies and steady state parameters of catalase and peroxidase activities. Strikingly, the deletion variants showed near to complete loss of catalase activity but retention of appreciable peroxidase activity. Concomitant with shift in activity was a change in heme coordination from predominantly hexacoordinate high‐spin to predominantly pentacoordinate high‐spin. These results emphasize the importance of distant protein structures and their interactions for fine‐tuning active site function, and in addition, point to factors beyond simple sequence differences which control active site function even some 30 Å from the active site. This project was supported by National Science Foundation (MCB‐ 0641614).