Mechanisms of oxidant generation by catalase.
The enzyme catalase converts solar radiation into reactive oxidant species (ROS). In this study, we report that several bacterial catalases (hydroperoxidases, HP), including Escherichia coli HP-I and HP-II also generate reactive oxidants in response to ultraviolet B light (UVB). HP-I and HP-II are identical except for the presence of NADPH. We found that only one of the catalases, HPI, produces oxidants in response to UVB light, indicating a potential role for the nucleotide in ROS production. This prompts us to speculate that NADPH may act as a cofactor regulating ROS generation by mammalian catalases. Structural analysis of the NADPH domains of several mammalian catalases revealed that the nucleotide is bound in a constrained conformation and that UVB irradiation induces NADPH oxidation and positional changes. Biochemical and kinetic analysis indicate that ROS formation by the enzyme is enhanced by oxidation of the cofactor. Conformational changes following absorption of UVB light by catalase NADPH have the potential to facilitate ROS production by the enzyme.
Heck
Diane E
DE
Department of Environmental Health Science, School of Health Sciences and Practice, New York Medical College, Valhalla, New York, USA. diane_heck@nymc.edu
Shakarjian
Michael
M
Kim
Hong Duck
HD
Laskin
Jeffrey D
JD
Vetrano
Anna M
AM
D000818:Animals; D002374:Catalase / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D016877:Oxidants / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D017382:Reactive Oxygen Species / Q000378:metabolism
D016877:Oxidants; D017382:Reactive Oxygen Species; D002374:Catalase