An ionizable active-site tryptophan imparts catalase activity to a peroxidase core.
Catalase peroxidases (KatG's) are bifunctional heme proteins that can disproportionate hydrogen peroxide (catalatic reaction) despite their structural dissimilarity with monofunctional catalases. Using X-ray crystallography and QM/MM calculations, we demonstrate that the catalatic reaction of KatG's involves deprotonation of the active-site Trp, which plays a role similar to that of the distal His in monofunctional catalases. The interaction of a nearby mobile arginine with the distal Met-Tyr-Trp essential adduct (in/out) acts as an electronic switch, triggering deprotonation of the adduct Trp.
Department of Microbiology, University of Manitoba , Winnipeg MB R3T 2N2, Canada.
Peter C
PC
Loewen
Xavi
X
Carpena
Pietro
P
Vidossich
Ignacio
I
Fita
Carme
C
Rovira
D002374:Catalase / Q000737:chemistry / Q000378:metabolism*; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D004789:Enzyme Activation; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D010544:Peroxidases / Q000737:chemistry / Q000378:metabolism*; D011789:Quantum Theory; D014364:Tryptophan / Q000737:chemistry / Q000378:metabolism*
D014364:Tryptophan; D010544:Peroxidases; D002374:Catalase