The molecular peculiarities of catalase-peroxidases.
In developing ideas of how protein structure modifies haem reactivity, the activity of Class I of the plant peroxidase superfamily (including cytochrome c peroxidase, ascorbate peroxidase and catalase-peroxidases (KatGs)) is an exciting field of research. Despite striking sequence homologies, there are dramatic differences in catalytic activity and substrate specificity with KatGs being the only member with substantial catalase activity. Based on multiple sequence alignment performed for Class I peroxidases, we present a hypothesis for the pronounced catalase activity of KatGs. In their catalytic domains KatGs are shown to possess three large insertions, two of them are typical for KatGs showing highly conserved sequence patterns. Besides an extra C-terminal copy of the ancestral hydroperoxidase gene resulting from gene duplication, these two large loops are likely to control the orientation of both the haem group and of essential residues in the active site. They seem to modulate the access of substrates to the prosthetic group at the distal side as well as the flexibility and character of the bond between the proximal histidine and the ferric iron. The hypothesis presented opens new possibilities in the rational engineering of peroxidases.
Institute of Biochemistry and Molecular Cell Biology, University of Vienna, Austria.
M
M
Zámocký
G
G
Regelsberger
C
C
Jakopitsch
C
C
Obinger
D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D002374:Catalase / Q000235:genetics; D020134:Catalytic Domain; D000458:Cyanobacteria / Q000737:chemistry / Q000201:enzymology / Q000235:genetics; D029968:Escherichia coli Proteins; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009161:Mycobacterium / Q000737:chemistry / Q000201:enzymology / Q000235:genetics; D010544:Peroxidases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D010944:Plants / Q000737:chemistry / Q000201:enzymology / Q000235:genetics; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D010544:Peroxidases; D002374:Catalase; C076136:catalase HPI; C051253:katG protein, E coli