α-Amylase: An Ideal Representative of Thermostable Enzymes

Abstract

The conditions prevailing in the industrial applications in which enzymes are used are rather extreme, especially with respect to temperature and pH. Therefore, there is a continuing demand to improve the stability of enzymes and to meet the requirements set by specific applications. In this respect, thermostable enzymes have been proposed to be industrially relevant. In this review, alpha-amylase, a well-established representative of thermostable enzymes, providing an attractive model for the investigation of the structural basis of thermostability of proteins, has been discussed.

Purification and Characterization of Extracellular, Polyextremophilic α-amylase Obtained from Halophilic Engyodontium album

“…Most of the enzymes are unable to perform the catalytic activity at high temperature values of 50-60ºC (27). The α-amylase in this study has been found to have optimum activity at 60ºC and retain more than 85% of its activity at high temperatures of 70-80ºC, which are considered as thermophilic range for enzymes (28,29).…”

Starch and Microbial α-Amylases: From Concepts to Biotechnological Applications

“…All known -amylases, with a few exceptions, contain a conserved Ca 2+ binding site which is located at the interface between domains A and B (Linden et al, 2003;Prakash & Jaiswal, 2010). In addition, -amylase produced by Bacillus thermooleovorans was found to contain a chloride ion binding site in their active site (Malhotra et al, 2000), which has been shown to enhance the catalytic efficiency of the enzyme, presumably by elevating the pKa of the hydrogen-donating residue in the active site (Prakash & Jaiswal, 2010).…”

“…In addition, -amylase produced by Bacillus thermooleovorans was found to contain a chloride ion binding site in their active site (Malhotra et al, 2000), which has been shown to enhance the catalytic efficiency of the enzyme, presumably by elevating the pKa of the hydrogen-donating residue in the active site (Prakash & Jaiswal, 2010). …”

“…Most known -amylases, with a few exceptions, contain a conserved Ca 2+ binding site (Linden et al, 2003;Prakash & Jaiswal, 2010) which make calcium be important to the enzyme activity. In manufacture of fructose syrup, the Ca 2+ ions inhibit the glucose isomerase enzyme used in the final step of the process (Tonkova, 2006) and may lead to the formation of inorganic precipitates which have deleterious effects on fermentation and downstream processing (Kelly et al, 2009).…”

The Effect of Metal Ions and Specific Chemical Reagents on the Activity of Aspergillus flavus var. oryzae and Bacillus subtilis α-Амylases

“…Більшість а-амілаз є металовмісними ферментами, активність яких може змінюватися у присутності іонів металів, які здатні виявляти акти вуючу чи інгібуючу дію. Зазвичай а-амілази містять у своїй структурі іони Са2+, які разом з іоном Na+ утворюють тріаду металів, що відіграє важливу роль у стабілізації білкової молекули та її стійкості до термічної інактивації [21].…”