New Insights into the Heme Cavity Structure of Catalase-Peroxidase: A Spectroscopic Approach to the Recombinant Synechocystis Enzyme and Selected Distal Cavity Mutants
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- 作者：Hendrik A. Heering ; Chiara Indiani ; Gü ; nther Regelsberger ; Christa Jakopitsch ; Christian Obinger ; and Giulietta Smulevich
- 刊名：Biochemistry
- 出版年：2002
- 出版时间：July 23, 2002
- 年：2002
- 卷：41
- 期：29
- 页码：9237 - 9247
- 全文大小：154K
- 年卷期：v.41,no.29(July 23, 2002)
- ISSN：1520-4995
文摘
Catalase-peroxidases (KatGs) are heme peroxidases with homology to yeast cytochrome cperoxidase (CCP) and plant ascorbate peroxidases (APXs). KatGs exhibit a peroxidase activity of broadspecificity and a high catalase activity, which strongly depends on the presence of a distal Trp as part ofthe conserved amino acid triad Arg-Trp-His. By contrast, both CCP and APX do not have a substantialcatalase activity despite the presence of the same triad. Thus, to elucidate structure-function relationshipsof catalase-peroxidases (for which no crystal structure is available at the moment), we performed UV-Vis and resonance Raman studies of recombinant wild-type KatG from the cyanobacterium SynechocystisPCC 6803 and the distal side variants (His123
ages/entities/rarr.gif">Gln, Glu; Arg119ages/entities/rarr.gif">Ala, Asn; Trp122ages/entities/rarr.gif">Phe, Ala). Thedistal cavity of KatG is very similar to that of the other class I peroxidases. A H-bond network involvingwater molecules and the distal Trp, Arg, and His is present, which connects the distal and proximal sidesof the heme pocket. However, distal mutation not only affects the heme Fe coordination state and perturbsthe proximal Fe-Im bond, as previously observed for other peroxidases, but also alters the stability ofthe heme architecture. The charge of the distal residues appears particularly important for maintaining theheme architecture. Moreover, the Trp plays a significant role in the distal H-bonding, much morepronounced than in CCP. The relevance of these findings for the catalase activity of KatG is discussed inlight of the complete loss of catalase activity in the distal Trp mutants.