Mokhtar T. Atallah

Relative efficiencies of a soluble and immobilized two-enzyme system of glucose oxidase and catalase.

Dual catalysts of varying glucose oxidase (EC 1.1.3.4) and catalase (EC 1.11.1.6) activities were constructed by immobilization of the enzymes to silanized nickel silica alumina with glutaraldehyde. The amount of product formed and the efficiency of the systems were determined using either of the enzymes to initiate the cyclic reaction. The former depends on the activity of both enzymes in the system while efficiency describes how well the second enzyme in the sequence utilizes the intermediate of the reaction. Efficiency was a function both of the ratio of the two activities and their absolute values. An increase in the activity of the second enzyme of the reaction sequence of a decrease in the activity of the first enzyme increased the efficiency. A higher efficiency was observed with higher absolute activities of the enzymes when the ratios of the enzyme increased the efficiency. A higher efficiency was observed with higher absolute activities of the enzymes when the ratio of the enzymes was constant. Dual catalysts were compared to mixed catalysts (each enzyme immobilized to separate particles) and to soluble, homogeneous systems at equal total activities. In general, the dual catalysts were superior to either of the others. Computer simulations of the reaction rates indicated that all experiments were performed in the lag period of the two-step reaction.

[32] The glucose oxidase—catalase system

Publisher Summary This chapter discusses the immobilization and assay procedure of the glucose oxidase–catalase system. Glucose oxidase is a glycoprotein having a molecular weight of approximately 150,000–180,0001; it contains 2 moles of flavin adenine dinucleotide per mole of enzyme and 11–16% carbohydrates. It has a pH optimum of approximately 5.5 to 5.7. The rate of oxidation of β-D-glucose is about 157 times faster than that of α-D-glucose. Important considerations in any assay technique, therefore, are the anomeric form of glucose present, the rate of mutarotation in the system compared to the rate of the reaction, and the extent of the reaction being measured. Glucose oxidase has been assayed manometrieally, polarographically, by differential conductivity, and by a coupled colorimetric assay involving peroxidase and o-dianisidine. A sensitive spectrofluorometrie analysis of H 2 O 2 has been developed using diacetyl dichlorofluorescein, which has possibilities of being adapted for the assay of GO x . The polarographic and conductivity methods avoid the difficulties of direct spectrophotometric assays when using particular matter in the assay mixture.

Connective tissue metabolism in muscular dystrophy. Early amino acid changes in collagen types isolated from the gastrocnemius muscle of developing dystrophic chicken embryos

The amino acid composition of all collagen types present in the gastrocnemius muscle of dystrophic chick embryos showed an altered profile at both day 14 and day 20 in ovo when compared with the controls. The changes observed at both day 14 and day 20 in ovo suggests that there is a removal of polar side-chains in dystrophic collagen and substitution with non-polar amino acids. The amino acid composition data between day 14 and day 20 indicated: (a) a decrease in hydroxylation (hydroxyproline and hydroxylysine) with a concurrent increase in proline and lysine and a decrease in the levels of arginine; (b) the levels of glycine and alanine did not change with age; and (c) the ratios of glycine to hydroxyproline and proline to hydroxyproline changed significantly in all dystrophic collagen types between day 14 and day 20. Contrast analysis results clearly showed that the changes in amino acid composition observed in each dystrophic type of collagen between day 14 and day 20 were not due to the effect of aging but to some other factor(s). This study provides more evidence that a problem lies in the biosynthesis of collagen present in developing muscles of dystrophic chick embryos, particularly with respect to the transcription or translation of procollagen genes and/or a failure in the processing and differentiation of collagen types.