Oxidase enzymes initial surface

Bioerosion occurs without change in molar mass of the bulk polymer, confirming that the microbial attack is initially in the oxidation-modified polymer surface and progression into the polymer depends on the continuation of peroxidation catalysed by transition metal ions. The bacterial colonies also produce oxidase enzymes e.g. cytochrome P-450) which produce superoxide and hydrogen peroxide from oxygen of the environment. The latter in turn gives highly reactive hydroxyl... 

This topic has been reviewed by Ingledew (55). The major components of the respiratory chain for T. ferrooxidans are a cytochrome oxidase of the Ci type, cytochromes c, and the blue copper protein rusticyanin. Initial electron transfer from Fe(II) to a cellular component takes place at the outer surface of the plasma membrane in the periplasmic space. The rate of electron transfer from Fe(II) to rusticyanin is too slow for rusticyanin to serve as the initial electron acceptor. Several proposals have been made for the primary site of iron oxidation. Ingledew (56) has suggested that the Fe(II) is oxidized by Fe(III) boimd to the cell wall the electron then moves rapidly through the polynuclear Fe(III) complex to rusticyanin or an alternative electron acceptor. Other proposals for the initial electron acceptor include a three-iron-sulfur cluster present in a membrane-bound Fe(II) oxidoreductase (39, 88), a 63,000 molecular weight Fe(II)-oxidizing enzyme isolated from T. ferrooxidans (40), and an acid-stable cytochrome c present in crude extracts of T. ferrooxidans (14). 

Attachment of glucose oxidase to the amino groups on the polypropylene beads was carried out as follows a 5-mL solution of glucose oxidase, containing 20 mg of enzyme in phosphate buffer, (0.5M, pH 7.5) was prepared. Thirty beads (PPB-NH2) were soaked in this solution for one hour. After removing the beads, the concentration of the remaining enzyme solution was measured and was used in calculating the initial concentration of the enzyme on the bead surface. 

Once a chemical reaches the viable epidermal layers, it may initiate a local effect, be absorbed into the circulation and produce an effect, or produce no local or systemic effects. The viable epidermis contains enzymes capable of metabolizing exogenous chemicals (Noonan and Wester 1983), including a substantial cytochrome P-450 system, esterases, mixed-function oxidases, and glucuronyltransferases. When the epidermal surface area is taken into account, then enzymatic activities of the epidermis can range from 80% to 240% of those in liver (Hotchkiss 1992). 

Amperometric ucose electrodes based on glucose oxidase undergo several chemical or electrochemical steps which produce a measurable current is related to the ucose concentration. In the initial steps, ucose converts the oxidized flavin adenine dimicleotide (FAD) center of die enzyme into its reduced form (FADH2). Because these redox centers are essentially electrical insulated within the enzyme molecule, direct electron transfer to the surface of a conventional electrode does not occur to any measurable d ree. The most common methodi of indirect measuring die amount of ucose present relies on the natural enzymatic reaction ... 

Similarly, a biosensor for sulfur dioxide has been designed based on the enzyme sulfite oxidase with cytochrome c as the electrOTi acceptor. Initially, sulfur dioxide, which is present in the gas phase, dissolves in the thin buffer layer that covers the surface of the biosensor where it is converted to sulfite ions. When sulfite is oxidized to sulfate, the active sites in the enzyme are reduced. The reduced form is then oxidized by cytochrome c. The reduced form of cytochrome c is monitored by electrochemical methods leading to the analytical signal. 

---