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Extracellular alpha-amylase from Streptomyces rimosus
B Vukelić1, A Ritonja, M Renko
1Department of Organic Chemistry and Biochemistry, Ruder Bosković Institute, Zagreb, Croatia.
Applied Microbiology and Biotechnology
|May 1, 1992
Summary
This study details the purification of an extracellular alpha-amylase from Streptomyces rimosus. The enzyme exhibits specific starch hydrolysis properties and structural characteristics, offering insights into microbial enzyme function.
Area of Science:
- Enzymology
- Microbiology
- Biochemistry
Background:
- Streptomyces rimosus is known for producing various bioactive compounds, including antibiotics like oxytetracycline.
- Extracellular enzymes such as alpha-amylase play crucial roles in microbial metabolism and substrate degradation.
Purpose of the Study:
- To purify and characterize the extracellular alpha-amylase from an oxytetracycline-producing strain of Streptomyces rimosus.
- To investigate the enzyme's biochemical properties, including its molecular mass, pI, catalytic activity, and substrate specificity.
Main Methods:
- Enzyme purification using standard biochemical techniques.
- Characterization of enzyme properties: pI, molecular mass (M(r)), amino acid homology, thermal stability, and Ca2+ ion effects.
- Enzymatic activity assays on starch hydrolysis at optimal pH.
Main Results:
- An acidic (pI 4.75) monomeric alpha-amylase with M(r) 43,000 was purified.
- The enzyme contains three cysteines crucial for catalytic activity and shows 57-67% homology with other Streptomyces amylases.
- Optimal starch hydrolysis occurs at pH 5.0-6.0, yielding specific oligosaccharides; enzyme is temperature-sensitive but Ca2+ partially stabilizes it.
Conclusions:
- The purified Streptomyces rimosus alpha-amylase is a distinct enzyme with specific catalytic and structural features.
- Understanding this enzyme's properties can contribute to knowledge of microbial carbohydrate metabolism and enzyme engineering.
- The enzyme's limited effect on most starch granules suggests specific substrate interactions.