Properties of a β-(1→4)-glucan hydrolase from Aspergillus niger

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Abstract
A [beta]-(1[long dash]4)-glucan hydrolase prepared from Aspergillus niger, as described by Clarke et Stone (1965a), showed a pH optimum in the range 4. 5-6 and Km 0. 25% when acting on a cellulose dextrin sulphate substrate. The hydrolase rapidly decreased the specific viscosity of carboxymethylcellulose with a small increase in the production of reducing sugars. The identity of the products of hydrolysis of cellotetraose, cellopentaose and their reduced analogues indicate a preferential cleavage of nonterminal glucosidic linkages. The enzyme may be described as [beta] -(l[long dash]4)-glucan 4-glucanohydrolase (EC 3.2.1.4). In addition to carboxymethylcellulose, cellulose dextrins, cellopentaose and cellotetraose the enzyme fraction hydrolysed lichenin, oat and barley glucans, ivory-nut mannan and a glucomannan from Konjak flour. No hydrolysis of wheat straw [beta]-(l[long dash]4)-xylan, Lupinus albus [beta]-(1[long dash]4)-galactan, pneumococcal type HI polysaccharide, chitin, hyaluronic acid, laminarin, pachydextrins, carboxymethylpachyman or [beta]-(1[long dash]3)-oligoglucosides was detected. The hydrolase showed no transglycosylase activity from cellodextrin or cellopentase substrates to glucose or methanol acceptors. The hydrolysis of cello-dextrins was inhibited completely by 1.0mM-Hg2+, 0. 7m[image]-phenyl-mercuric nitrate and 1. 0m[image]-iodine.