The roles of the N-linked carbohydrate chain of rice alpha-amylase in thermostability and enzyme kinetics.

The thermostability and kinetics of starch hydrolysis were compared between a rice alpha-amylase isozyme Amy1A and its mutant enzyme that lacks an N-linked carbohydrate chain. Elimination of the N-glycosylation site in Amy1A reduced the thermostability of the enzyme. The temperature dependence of the kinetic parameters (Vm and Km) and substrate recognition of the enzymes were also affected by elimination of the N-glycosylation site. These results suggest that the N-linked carbohydrate chain of Amy1A has important roles in the thermostability and reaction kinetics of the enzyme.