Cell-free extracts of a Flavobacterium sp.efficiently convert 2,3-dibromopropanol into glycerol via the sequence: dibromopropanol -epibromohydrin -> dihydroxybromopropane -* glycidol -glycerin. The c X^Varbon-halogen bonds are present in a wide array of biocides and anesthetics. Moreover, -halo acids are widely employed as enzymatic inhibitors (Webb, 1966;Leasure, 1964). Indeed, because of the toxicity of organic halides and their inhibitory capacities it is understandable that the full scope of enzymatic dehalogenation remains to be portrayed. Nevertheless some remarkable transformations have been recorded. Thus, carbon tetrachloride is reduced to chloroform by dogs (Butler, 1961) and converted into carbon dioxide by monkeys (McCollister et al., 1951) and rat liver homogenates (Rubinstein and Kanics, 1964). The insecticide

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.

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Resting cell suspensions of a soil Pseudomonus sp readily metabolize vinyl chloride Studies with a combination of I3C and I4C labeled vinyl chloride and metabolites establish that the initial dehalogenation step formally entails a direct hydroxylation of the C-C1 bond to produce acetaldehyde This substance undergoes biochemical oxidation at both the carbonyl and the methyl carbons to produce acetic acid and hydroxyacetaldehyde These are both further oxidized by the organism to hydroxyacetic acid (glycolic acid), and the latter is converted to carbon dioxide The rate of C1 liberation from vinyl chloride is a function of growth conditions Cells grown on 3 chloropropanol carry out the dehalogenation of vinyl chloride with a t,,, of 1 3 h at a cell density of 0 1 g/ml

In contrast to its lethargy at physiological pH, horse heart cytochrome c can be oxidized at room temperature by the axial inner sphere oxidant bromomalononitrile (BMN) at higher acidities. The following stoichiometry obtains: 2Fe11 c + BrCH(CN2) + H+ leads to 2FeIII c + CH2(CN)2 + Br-, and the rate law is given by: rate = k2(FeIIc)(BMN). At an ionic strength of 1.0 (KCl), second-order rate constants vary from 300 l. per mol per sec (pH 2-3) to 0(pH 9). Below pH 6 there is a noticeable increase in rate with ionic strength while there is no specific salt effect for the process. At pH 7.4 there is no influence of added salt (0.01-1.0 M) upon the slow rate of reaction. The vast changes in rate occur over a pH region (3-6) in which only very minor changes in the visible spectrum of the cytochrome are manifest. The results are interpreted in terms of a conformational isomerism of cytochrome c in which the effective redox geometry alters from a predominantly "short C" form (in which an axial position is available for substitution) at lower pH's to a predominantly "C" form (axial positions encumbered) in the physiological region. At 5 degrees, pH 7.4, both hemes of beef heart cytochrome oxidase are oxidized by the addition of BMN (k2 = 29 plus or minus 3 l. per mol per sec). However, the reaction is inhibited by potassium cyanide and the protein containing iron(II) cyt alpha along with the cyano adduct of iron(II) or iron(III) cyt alpha3 is inert. The results demonstrate cytochrome alpha3 as the site of reaction and that alpha reduces alpha3 in the process. Cytochrome oxidase does catalyze the oxidation of cytochrome c with BMN as substrate. Taken together the results provide additional support for a recent theory and they demonstrate BMN to be an efficient probe for the effective redox geometry of a hemoprotein in solution.