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Cloning and characterization of an intracellular isoamylase gene from Pectobacterium chrysanthemi PY35
1Division of Applied Life Science, Gyeongsang National University, Chinju, 660-701, Korea.
Abstract:
The gene encoding an intracellular isoamylase from the Pectobacterium chrysanthemi PY35 was cloned in Escherichia coli DH5alpha and sequenced. The isoamylase gene (amyX) had an open reading frame of 1974 bp encoding 657 amino acid residues with a calculated molecular weight of 74,151 Da. The molecular weight of the enzyme was also estimated to be 74 kDa by activity staining of a SDS-PA gel. Isoamylase from P. chrysanthemi PY35 had 59% pairwise amino acid identity with glycogen debranching enzyme from E. coli and contained the four regions conserved among all amylolytic enzymes. The isoamylase was optimally active at pH 7 and 40 degrees C. AmyX hydrolyzed alpha-1,6-glycosidic linkages of amylopectin, while did not hydrolyze alpha-1,4-glycosidic linkages of amylose.
Insights
Researchers cloned and sequenced the isoamylase gene (amyX) from Pectobacterium chrysanthemi PY35. The resulting enzyme efficiently hydrolyzes alpha-1,6-glycosidic linkages in amylopectin, showing potential for industrial applications.
Area of Science:
- Enzymology
- Molecular Biology
- Microbial Biochemistry
Background:
- Intracellular isoamylases are enzymes involved in carbohydrate metabolism.
- Understanding the properties of isoamylase from Pectobacterium chrysanthemi PY35 can provide insights into starch hydrolysis mechanisms.
Purpose of the Study:
- To clone and characterize the gene encoding intracellular isoamylase from Pectobacterium chrysanthemi PY35.
- To determine the biochemical properties and substrate specificity of the purified isoamylase.
Main Methods:
- Cloning of the isoamylase gene (amyX) into Escherichia coli DH5alpha.
- DNA sequencing to determine the open reading frame and predict amino acid sequence.
- SDS-PAGE with activity staining to estimate molecular weight.
- Enzyme activity assays to determine optimal pH, temperature, and substrate specificity.
Main Results:
- The amyX gene consists of a 1974 bp open reading frame, encoding a 657-amino acid protein with a calculated molecular weight of 74,151 Da.
- The enzyme exhibited optimal activity at pH 7 and 40°C.
- Isoamylase specifically hydrolyzed alpha-1,6-glycosidic linkages in amylopectin but not alpha-1,4-glycosidic linkages in amylose.
Conclusions:
- The cloned isoamylase (AmyX) from P. chrysanthemi PY35 is a functional enzyme with specific activity towards alpha-1,6-glycosidic bonds.
- The enzyme shares conserved regions with other amylolytic enzymes, suggesting a common catalytic mechanism.
- AmyX demonstrates potential for applications requiring selective hydrolysis of branched starch structures.
