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Starch-binding domain affects catalysis in two Lactobacillus alpha-amylases
R Rodríguez-Sanoja1, B Ruiz, J P Guyot
1Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, UNAM A. P. 70228, 04510 Mexico City, Mexico. romina@correo.biomedicas.unam.mx
Lactobacillus alpha-amylases with unique starch-binding domains (SBDs) show varying hydrolytic capabilities. L. amylovorus amylase is significantly more efficient than L. plantarum amylase in starch hydrolysis.
Area of Science:
- Enzymology
- Microbial biochemistry
Background:
- A novel starch-binding domain (SBD) characterized by tandem repeats and approximately 500 amino acids was identified in alpha-amylases from Lactobacillus amylovorus, Lactobacillus plantarum, and Lactobacillus manihotivorans.
- These lactobacillus alpha-amylase genes exhibit over 98% sequence identity, yet their SBD structures display notable differences.
Purpose of the Study:
- To investigate the impact of structural variations in SBDs on the hydrolytic efficiency of Lactobacillus alpha-amylases.
- To compare the enzymatic activity and substrate adsorption of L. amylovorus and L. plantarum alpha-amylases.
Main Methods:
- A kinetic study was conducted using purified alpha-amylases from L. amylovorus and L. plantarum.
- Enzyme activity was assessed on various granular and gelatinized starch substrates.
Main Results:
- L. amylovorus alpha-amylase demonstrated an average of 10-fold greater efficiency in hydrolyzing tested polymeric starches compared to L. plantarum alpha-amylase.
- Adsorption capacities of the two enzymes on starch substrates showed only minor differences.
Conclusions:
- Structural variations within the large SBDs of Lactobacillus alpha-amylases significantly influence their catalytic efficiency.
- L. amylovorus alpha-amylase possesses superior starch hydrolyzing capabilities over L. plantarum alpha-amylase, despite similar gene sequence identity and minor differences in adsorption.
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