Extraction and characterization of alpha-amylase inhibitor from some cereals and legumes

ABSTRACT

Alpha-amylase inhibitor extracted from different sources, i.e., wheat grains [Sohag 2 and Giza 164], legume seeds such as cow pea [Carim 7 and Giza 3], and kidney bean [Giza 6 and Giza 133] was purified and tested for activity using human salivary and pancreatic alpha-amylase. Results showed that the alpha-amylase inhibitor activity from samples studied were 120 to 285 unit / mg protein. The inhibitor was found to be stable at pH range from 2 to 4. It was also stable to digestion by proteolytic enzymes [pepsin and trypsin]. The inhibition was faster at 37°C than at 25°C, The results showed that the degree of thermal stability of alpha-amylase inhibitor extracted from kidney bean [Giza 133] was at 35-37°C, activity was decreased on 50°C for 5 hr. Increased of pre-incubation time between inhibitor and both alpha-amylase enzymes at 37°C increased the rate of inhibition of these enzymes and the complex formation between them from 60 - 80% in 30 min, while addition of these enzymes to the mixture containing inhibitor and substrate [without pre-incubation] decrease the percent inhibition. Therefore, an evidence of specific interference of the alpha-amylase inhibitor with starch availability was established. Such possibilities will have valuable interest in the field of special dietary food preparations for diabetes and over weight reduction purposes: