Stability and conformational changes of transglutaminase from Streptomyces hygroscopicus in ethanol–aqueous medium

Effect of ethanol on the stability and conformational changes of transglutaminase from Streptomyces hygroscopicus (MTGase) was studied. The presence of 10% ethanol increased 20% activity and about 85% activity was lost in 50% ethanol–aqueous solution after incubation for 60 min at 25 °C. The Km and Vmax of the enzyme were 63.13 mmol/L and 14.02 μmol/(mg protein min) in the presence of 10% ethanol, and 34.20 mmol/L and 0.68 μmol/(mg protein min) in the presence of 30% ethanol, respectively. The results of spectral determination indicated that MTGase did not undergo significant structural changes in 10% ethanol–aqueous solution. At ethanol concentration of 40%, the α-helix structure content of the enzyme decreased from 20.5 ± 0.5% to 14.3 ± 0.7% and the unordered structure content increased from 46.4 ± 0.5% to 72.6 ± 1.7%. Some polyhydroxy compounds could improve the stability of the enzyme at high ethanol concentration.