The desirable salt bridges in amylases: Distribution, configuration and location

The α-amylases are the most widely used industrial enzymes, and are particularly useful as liquifying enzymes in industrial processes based upon starch. Since starch liquefication is carried out at evaluated temperatures, typically above 60 °C, there is substantial demand for thermostable α -amylases. Most naturally occurring α -amylases exhibit moderate thermostability, so substantial effort has been invested in attempts to increase their thermostability. One structural feature that has the potential to increase protein thermostability is the introduction of salt bridges. However, not every salt bridge contributes to protein thermostability. The salt bridges in amylases have their characteristics in terms of distribution, configuration and location. The summary of these features helps to introduce new salt bridges based on the characteristics. This review focuses on salt bridges of α-amylases, both naturally present and introduced using mutagenesis. Its aim is to provide a bird's eye view of distribution, configuration, location of desirable salt bridges.