Chemical modification of wheat β-amylase by trinitrobenzenesulfonic acid, methoxypolyethylene glycol, and glutaraldehyde to improve its thermal stability and activity.

The amino groups of wheat β-amylase (WBA) were modified by 2,4,6-trinitrobenzenesulfonic acid (TNBS), 2,4-bis (O-methoxypolyethylene glycol)-6-chloro-s-triazine (mPEG), and glutaraldehyde (GA) to improve its thermal stability and activity. Modification of WBA by 5mM TNBS, 4.8μM mPEG and 11 mM GA improved its T50 (the temperature at which 50% of its activity is lost after 30 min of incubation) from 47 ± 1°C to 48 ± 2, 55 ± 2, and 54 ± 2°C, respectively. The catalytic activity of WBA was reduced by 15% and 59% with modification by 5mM TNBS and 11mM GA, respectively. In all cases, the enhancement of thermostability of modified WBA was entropically driven. The activity of WBA modified by 4.8μM mPEG was enhanced by 39% at 25°C. Therefore, the thermal stability of WBA was significantly improved by modification with mPEG, GA and slightly by TNBS and its catalytic activity was enhanced by mPEG.