Comparative study of external and internal β-glucosidases and glucoamylase of Arxula adeninivorans

✍ Scribed by Dr. Roland Büttner; RÜDiger Bode; Dieter Birnbaum

• Book ID: 102388587
• Publisher: John Wiley and Sons
• Year: 1991
• Tongue: English
• Weight: 392 KB
• Volume: 31
• Category: Article
• ISSN: 0233-111X
• DOI: 10.1002/jobm.3620310606

✦ Synopsis

Properties of external and internal P-glucosidases and glucoamylase of Arxula adeniniuorans were compared. For the purification of enzymes, the C-catabolite derepression mutant SBUG 724/41 was used. The following K,-values for P-glucosidases with cellobiose as substrate were measured: 14.3 mM (internal @-glucusidase I), 4.1 m M (external ~-glucusidase I), 5.0 mM (internal P-glucosidase II), 3.0 mM (external P-glucosidase 11). The K,-values of the glucoamylase for maltose were 4.6 mM (internal enzyme), 11.1 mu (external enzyme), and for starch 0.32 g/l and 1.2 g/l, respectively.

Both external P-glucosidases showed a relatively sharp pH-optimum in a range from 4.5 to 5.5 while that of internal enzymes was between 5.5 and 6.0. No differences were obtained between pH-optima (4.5 -5.5) of internal and external glucoamylase. The temperature optimum values of internal P-glucosidase I (40 "C) and of internal P-glucosidase I1 (50 "C) were remarkably low compared with those of the external 8-glucosidases (60-63 "C) and both glucoamylases (60 "C).

Molecular mass of 570 kD for the external and of 290 kD for the internal /I-glucosidase I, on the one hand, and of525 kD and 180 kD for the internal P-glucosidase I1 on the other hand were determined. The external glucoamylase consists of two subunits with a molecular mass of 110 kD. After deglycosylation a molecular mass of 76 kD was measured, indicating a carbohydrate content of 30%, whereas for the internal enzyme, a molecular mass of 95 kD was estimated.