Sodium periodate enzyme activation

Ornithine Decarboxylase Assays. The double-chamber assay system of Moskal and Basu (59) was used to measure enzyme activity in the form of L C] carbon dioxIHe evolution. The assay conditions of O Brien and Diamond (60) were used and consisted of the following components (in micromoles, unless otherwise stated) in a total volume of 100 jul sodium phosphate buffer, pH 7.2, 5.0 EDTA, 1.0 dithiothreitol, 5.0 pyridoxal-5 -monophosphate, 0.2 L-ornithine (specific activity 0.5 x 10° cpm/-jumole), 0.1 and protein, 0.1-0.5 mg. Incubations were carried out at 37°C for 60 min, and the reactions were terminated by the addition of 200 jul of 2M sodium citrate followed by a post-incubation period of 3 hours at 37°C to insure maximal release of radiolabeled carbon dioxide. 

None of the systems lost any enzyme activity during 24 h of continuous pumping of glucose solution (1 mM) at 2.3 ml/min. Moreover the various membranes when stored at 4P C in sodium dihydrogen phosphate (pH 7) still responded to substrate (70% of the signal for a new electrode) with intermittent use over a period of about 4 months after the fabrication (4). 

The thermal inactivation assays of soluble YLL and immobilized preparations on octyl-agarose, octadecyl epabeads and MANAE agarose were carried out incubating the same amount of lipase in three different buffers at 45°C 25 mM sodium acetate pH 5, 25 mM sodium phosphate pH 7 and 25 mM sodium carbonate pH 9. Periodically, residual enzyme activity was estimated by hydrolysis of pNPB. Soluble enzyme was submitted to the same conditions. 

The carbohydrate moiety of j3-D-fructofuranosidase of Candida utilis was suggested to be localized at certain sites of the enzyme protein. The oxidation of the sugar moeity with periodate to a certain extent had no effect on the enzyme activity, but the stability of the enzyme was decreased. This partially oxidized enzyme bound hide powder or nylon powder and the enzyme activity was retained. The enzyme was shown to be divided into glycoprotein sub-units of a similar molecular size when heated in the presence of sodium dodecyl sulphate. The enzyme did not dissociate upon treatment with reducing agent such as mercaptoethanol. 

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