L-Aspartate oxidase from Sulfolobus tokodaii: immobilization studies

L-Amino acid oxidases (LAAOs, EC 1.4.3.2) catalyze the stereospecific oxidative deamination of L-amino acids to a-keto acids, ammonia and hydrogen peroxide. In our labs Laspartate oxidase from the thermophilic archaea Sulfolobus tokodaii (StLASPO, EC 1.4.3.16) has been efficiently produced as recombinant protein in E. coli in the active form as holoenzyme and fully characterized. The enzyme is active only on L-aspartate and on L-asparagine and it’s absolutely stereoselective. StLASPO shows a remarkable stability: up to 80 °C in the 7 – 10 pH range. Plotting the activity (on L-aspartate) against temperature in the 25 – 95 °C range, an increase with no evidence for any plateau or decrease up to 80 °C was apparent. The activity of the enzyme as a function of pH shows a bell-shaped behavior: it is maximal at about pH 10.