Characterization of a Novel Glucoamylase from the Thermoacidophilic Archaeon Picrophilus torridus Heterologously Expressed in E. coli

There is an interest in the production of heat‐ and acid‐stable enzymes due to their potential application in various industrial fields, particularly in the food, brewery, and textile industries. Microorganisms living in extreme habitats are a good source for such enzymes as they enable to perform b...

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Bibliographic Details
Published in:Engineering in life sciences 2006-06, Vol.6 (3), p.311-317
Main Authors: Schepers, B., Thiemann, V., Antranikian, G.
Format: Article
Language:English
Subjects:
Biocatalysis
Biological and medical sciences
Biotechnology
Enzymes
Escherichia coli
Fundamental and applied biological sciences. Psychology
Genetic engineering
Glucose
Picrophilus torridus
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Summary:There is an interest in the production of heat‐ and acid‐stable enzymes due to their potential application in various industrial fields, particularly in the food, brewery, and textile industries. Microorganisms living in extreme habitats are a good source for such enzymes as they enable to perform biotransformation reactions under non‐conventional conditions. After the complete genome analysis of the thermoacidophilic archaeon Picrophilus torridus (optimal growth at pH 0.7 and 60 °C) a number of genes were identified that encode for amylolytic enzymes, proteases, and esterases. A gene encoding an intracellular glucoamylase from P. torridus was cloned and successfully expressed in E. coli. The recombinant enzyme was purified to homogeneity with a yield of 37 % by heat treatment, anion exchange, and gel filtration chromatography. As revealed by non‐denaturating PAGE, the active enzyme forms a homotetramer (73 kDa/subunit). The recombinant glucoamylase shows activity between 30 °C and 65 °C and a pH of between 4.5 and 6.5. Interestingly, the enzyme shows unique substrate specificity compared to already known glucoamylases. In addition to the hydrolysis of branched and linear α‐glucans, the purified enzyme preferentially attacks maltotriose. The Vmax for maltotriose (10 U/mg) is even higher than the Vmax for starch (8 U/mg). The high maltotriose preference of this archaeal enzyme is unique among all glucoamylases described so far. The production of glucose from starch is a process preferentially run at high temperatures and low pH, for which stable amylolytic enzymes are needed in ton scales. Therefore, thermoacidophiles are an interesting source for robust enzymes enabling biocatalysis under non‐conventional conditions.
ISSN:1618-0240
1618-2863
DOI:10.1002/elsc.200620131