Effect of Preparation Conditions of Enzyme-Encapsulating W/O/W Emulsion on Enzymatic NAD+-Recycling in the Emulsion

概要

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The effects of the preparation conditions of W/O/W emulsion on the NAD+-recycling reaction catalysed by yeast alcohol dehydrogenase (ADH) and malate dehydrogenase (MDH) encapsulated in W/O/W emulsion were experimentally studied. The main results were as follows. 1) The first-stage emulsifying agent, such as Span80, protects the enzyme from enzymatic activity loss which is caused when the enzyme is subject to the shearing force of a homomixer or is in contact with an organic agent during preparation of the emulsion. 2) Addition of soybean lecithin or cholesterol to Span80 makes W/O/W emulsion rigid and stable. Moreover, the additives increase the reaction rate of enzymatic NAD+-recycling. 3) Addition of soybean lecithin increases the stability of the enzyme in the emulsion. 4) Apparent enzymatic reaction rate in the emulsion depends on the solubilities of ethanol and acetaldehyde in the oil phase of the emulsion.It is suggested that enzymatic activity is enhanced by the interaction between the phospholipid of lecithin and the enzyme which is in the lipid membrane of the W/O/W emulsion, and also by the localization of enzymes or substrates in the compartment of the microenvironment of the emulsion. It is also pointed out that the study of enzyme-containing emulsion may be useful as a model of a membrane-bound enzyme or a multi-enzyme system in a living cell.