In vitro activity and stability of pure human salivary aldehyde dehydrogenase.

Human salivary aldehyde dehydrogenase (HsALDH) appears to be the first line of defence against toxic aldehydes contained in exogenous sources and is important for maintaining healthy oral cavity and protection from oral cancer. Here, the activity and stability of purified hsALDH has been determined under different conditions such as temperature, in presence of denaturants [Urea and guanidine hydrochloride (GnHCl)] and in the presence of salt (NaCl). The pure enzyme exhibited low stability when stored at room temperature (25°C) as well as at low temperature (4°C). 10% glycerol significantly improved its storage stability, particularly at 25°C. HsALDH was observed to have very low thermal stability. At higher temperatures, the enzyme gets unfolded and loses its activity quite rapidly. Further, the enzyme is unstable in the presence of denaturants like urea and GnHCl which unfold the enzyme. Salt (NaCl) has an activating effect on the enzyme, resulting from perhaps due to some conformational changes in the enzyme which facilitates the catalysis process. HsALDH proved to be a labile enzyme under in vitro conditions and certain additives like glycerol and NaCl can improve the activity/stability of the enzyme. Hence, a stabilizing agent is required to use the enzyme in in vitro studies.