Oxidation of heme proteins by alkyl halides: a probe for axial inner sphere redox capacity in solution and in whole cells

Abstract

Iron(II) porphyrins in homogeneous solution, in heme proteins, and in intact human erythrocytes and lysed cells are oxidized by certain alkyl halides to the corresponding iron(III) complexes at room temperature. The mechanism established for the oxidation of hemes in homogeneous solution operates at all levels of biological integrity. It is an axial inner sphere process. Deoxyhemoglobin has about the same reactivity within and without cells. The speed of the reaction with the proteins is primarily governed by the steric accessibility to iron. The reactivity of an array of iron(II) proteins accords well with theoretical prediction. In contrast the reactivity of cytochrome b5 does not. An examination of the oxidation and reduction of this protein was additional mechanistically defined reagents (trinitrobenzene and hydroquinone) shows it to be in the G rather than C conformation. The unusual redox characteristics of this protein can be rationalized on this basis.

Biodehalogenation: The Kinetics and Rates of the Microbial Cleavage of Carbon-Halogen Bonds

“…In all of our work, halide ion is measured by direct potentiometry and rates are based upon it rather than substrate disappearance or oxygen consumption. In some cases a direct spectrophotometric measure of enzyme oxidation in intact cells was possible [23,24]. In general, the rate of disappearance of substrate parallels that for halide release, but this is not always so.…”

“…Our major focus has been on bacteria because of the rich diversity of chemistry they exhibit and because they are abundantly present in soil. Some more limited work with human red blood cells was also undertaken [23]. While each cell may have a best set of conditions under which it most readily transforms organic halides, we have opted for a standardized experimental approach.…”

Buffering acid precipitates, reducing soil erosion, and reclaiming toxic soil in the advent of global human carrying capacity

“…In addition, numerous enzymes and combinations of iron and certain organic substances capable of dehalogenating 65 and decomposing 66 industrial wastes, pharmaceuticals, biocides and so on are present in soil.…”

Analysis of blood proteins on protein arrays with a spectral surface plasmon resonance biosensor

“…Although Hb does not function physiologically as an electron carrier, it is an ideal model molecule for the study of electron transfer reactions of heme proteins because of its commercial availability, moderate cost, and known and documented structure. Furthermore, Hb has enzyme-like oxidative [3] and reductive catalytic activity [4,5], similar to the heme enzyme cytochrome P450 S [6]. Thus, Hb incorporated into stable films modified on electrodes, which can enhance electron transfer, may be useful as a model for heme enzymes, and also for biosensors [7,8] and electrochemical biocatalysis [9].…”