Purification and properties of three cellobiases from Aspergillus niger A20

Authors: Abdel-Naby, Mohamed; Osman, Mona; Abdel-Fattah, Ahmed

Source: Applied Biochemistry and Biotechnology, Volume 76, Number 1, February 1999 , pp. 33-44(12)

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Abstract:

Three cellobiases, here called cellobiase A, B, and C, from the culture filtrate of Aspergillus niger A20, were purified by precipitation with ammonium sulphate, gel filtration through Sephadex G-75, and column chromatography of DEAE-cellulose. The purified enzymes were homogeneous on polyacrylamide disk electrophoresis. The mol wt of the purified enzymes were estimated by SDS-gelelectrophoresis to be 88,000, 80,000, and 71,000 for cellobiases A, B, and C, respectively. The enzymes were active at pH 4.5 and 55-60°C. The pattern of their aminoacid compositions showed high contents of aspartic acid, glutamic acid, threonine, serine, and glycine. The apparent K_m values for cellobiose were 0.9, 1.63, and 1.0 mM for cellobiases A, B, and C, respectively. Calcium ions stimulated cellobiases B and C, and Co²⁺ and Mg²⁺ ions stimulated cell obiase A. The purified enzymes hydrolyzed cellobiose and aryl-β-d-glucosides, but they had no action on sucrose, maltose, and cellulose. The three cellobiases catalyzed transglycosylate reaction, and the major product formed from cellobiose was tetramer of glucose.

Keywords: Aspergillus niger; cellobiase; purification; properties

Document Type: Research article

DOI: http://dx.doi.org/10.1385/ABAB:76:1:33

Affiliations: 1: Department of Chemistry of Natural and Microbial Products, National Research Centre, Dokki, Cairo, Egypt,

Publication date: 1999-02-01