The enzymic degradation of pectin and other polysaccharides. II—Application of the ‘Cup‐plate’ assay to the estimation of enzymes

Abstract

The agar cup-plate ' diffusion technique has been applied to the quantitative determination of enzyme activity, principally to amylase, polygalacturonase, cellulase. protease and pectin-esterase. With all enzymes so far examined, the relationship between diameter of zone and log(amount of enzyme) is linear over a wide range, and may be used for the quantitative estimation of the enzymes. The cup-plate assay of polygalacturonase, like viscometric methods, measures the initial destruction of the colloidal properties of pectic acid, and, owing t o the complex nature of polygalacturonase, bears no simple relationship t o the assay of polygalacturonase by the estimation of glycosidic hydrolysis. H. Experiments are described in which flour stored in jute bags, the fabric of which had been impregnated with insecticides, was exposed to infestation by the species Ephestia kuhniella, Ptinus tectus and Tribolium confusum. The use of 1 % (w/w) of DDT in the fabric provided good protection against the first two named, and fair, but by no means absolute, protection against T . confusum. Transfer of insecticide to the flour occurred to an extent sufficient to be classed as contamination.

Postharvest calcium chloride treatments do not help to increase shelf-life of bananas

“…Cup plate assay [11] was used to estimate pectinase activity modified as already described [10]. The sterile test medium in petri plates contained 1% sodium polypectate (substrate), 0.5% (w/v) ammonium oxalate and 2% agar, in appropriate buffer solution (100 mL) to obtain a pH range of 5 to 9; 0.1 M phosphate buffer (pH 5-6); 0.1 M Tris-HCl (pH 7-9).…”

A Comparison of the Polygalacturonases Produced in vivo and in vitro by Penicillium expansum Thom.

“…PG in the fractions collected from the various columns was assayed by a cup-plate method (Dingle, Reid & Solomons, 1953). A dilution series of the enzyme applied to…”

The Partial Purification and Properties of Endopolygalacturonase and -L-Arabinofuranosidase secreted by Sclerotinia fructigena

“…Activity was expressed as I f t where t was the time (min.) for 50 yo decrease in viscosity; (c) an agar plate assay, as described by Dingle, Reid & Solomons (1953) was extensively used for semi-quantitative estimations during purification. The external diameter of the white ring obtained on the pectate agar plate was proportional to the logarithm of the enzyme concentration over a range of dilutions.…”