Abstract
We have described, very recently, that cytochrome b5 (Cb5) is able to acquire a peroxidase-like activity in extreme alkaline media, when a hemichromic state is attained. At pH 4, Cb5 is mainly in a high-spin state (protein unfolding occurs and heme is released from the peptide chain) and its peroxidase activity is weak when compared with the one measured to pH 12. A structural characterization of Cb5 alkaline transition allowed us to reveal several parameters that might affect its stability and activity. H1NMR studies above pH 11 indicate the existence of a heme spin alterations that correlates with formation of tyrosinate anion, suggesting conformational changes at the heme crevice. Spectroscopic data support the interaction of Cb5 with imidazole above pH 11 and suggest the appearance of a binding site in the protein that allows accessibility of substrates to the heme. Our study, accordingly with other reports, shows acquisition of enzymatic activities when non-native states are acquired, before unfolding.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
