Beta (β)-Galactosidase
| Autor: | R.E. Huber |
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| Rok vydání: | 2013 |
| Předmět: | |
| DOI: | 10.1016/b978-0-12-374984-0.00149-2 |
| Popis: | β-Galactosidase ( Escherichia coli ) is a tetrameric enzyme of historical and scientific importance. The primary natural substrate is lactose. It is converted to either galactose and glucose (hydrolysis) or allolactose (galactosyl transfer). Allolactose is also a substrate. It is converted to galactose and glucose and thus is a transient product. The enzyme specifically attacks β-galactosides via intermediate formation of a covalent bond. A general acid/base catalytic group (Glu461) and a nucleophile (Glu537) are involved and the transition state is a half chair with a 4 H 3 conformation. Mg 2+ and Na + are important for activity. A loop at the active site opens and closes and changes the binding properties for substrate and transition state, thereby helping facilitate the reaction. |
| Databáze: | OpenAIRE |
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