Biocatalyst replacement by mimetics in bioconversions: Can the time-scale be predicted?

Enzyme mimics (mimetics) include abzymes (catalytic antibodies), RNA molecules (ribozymes), and enzyme analogues synthesized upon a polypeptide backbone structure (synzymes). Also, there is a variety of model systems such as the zeolite-membrane systems containing metal complexes, which mimic cytochrome P-450. Enzymes are being subjected to redesign procedures to introduce desired features such as thermostability that could improve their industrial usefulness: but even such novel enzymes may not be able in the near future to out-perform the enzyme mimics in all circumstances, such as at temperatures above about 120°C or under completely non-aqueous conditions.     

Assay-increment and solubilisation of α-glucosidase and invertase in disruption of brewers' yeast

A variety of disruption techniques were used on brewers' yeast with subsequent estimation of the additional (assay-increment) α-glucosidase and invertase made accessible to p-nitrophenylglucoside (PNPG) and sucrose, respectively, in the total disruptate. The extent of actual solubilisation of these two enzymes in the 0.75 M potassium phosphate buffer (pH 6.5) present, was also measured. Extensive release (i.e. solubilisation) of α-glucosidase was achieved using ultrasonication or ethyl acetate autolysis, and here differential release of α-glucosidase over invertase was large. Extensive release of both α-glucosidase and invertase was obtained with snail gut enzyme and toluene (papain) autolysis, while air drying released some invertase but destroyed 80% of the α-glucosidase. The assay-increment, over intact yeast values, for α-glucosidase in total disruptate, which is due to increased accessibility of PNPG to this enzyme, was high for salt autolysis and toluene (papain) autolysis but was low for the Mickle shaker and the Potter-Elvehjem homogeniser. No increment was observed using the X-press, although solubilisation of α-glucosidase was moderately good. Increment, over intact yeast values, for invertase assay in total disruptate was highest with ultra-sonication and air drying, but was nevertheless generally low owing to almost complete availability of this cell wall enzyme for assay—but not for isolation—in intact yeast.