ISSN:
0006-3592
Keywords:
Aspergillus awamori
;
glucoamylase
;
kinetic
;
thermostability
;
Saccharomyces cerevisiae
;
Chemistry
;
Biochemistry and Biotechnology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Process Engineering, Biotechnology, Nutrition Technology
Notes:
Asn182 → Ala Aspergillus awamori glucoamylase expressed in Saccharomyces cerevisiae had a first-order thermodeactivation coefficient 40% that of wild-type glucoamylase at pH 4.5 between 60° and 65°C, caused by the elimination of an Asn - Gly sequence subject to deamidation and eventual chain breakage. Above 70°C, and at pHs 3.5 and 5.5, thermodeactivation coefficients of wild-type and mutant enzymes were roughly equal, because the fastest deactivation mechanism was no longer deamidation. The mutation had little effect on the enzyme's optimal pH for activity and subsite map, or on the glucose yield from starch dextrin hydrolysis. During enzyme production by yeast fermentation, highest cell densities and activities of wild-type and mutant glucoamylases were attained after a period of glucose starvation, followed by a second addition of glucose. © 1994 John Wiley & Sons, Inc.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/bit.260430113
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