고온성 알콜발효 효모의 Alcohol Dehydrogenase의 특성

The characteristics of alcohol dehydrogenase (ADH, EC 1.1.1.1, alcohol:NAD oxidoreductase) of thermotolerant alcohol-producing yeasts, Saccharomyces cerevisiae RA-74-2 and Kluyveromyces marxianus RA-912, were compared with that of mesophilic S. cerevisiae D, an industrial strain. Under anaerobic culture condition, both S. cerevisiae RA-74-2 and D had similar level of ADH activity at 30$\circ$C, and the activity of S. cerevisiae RA-74-2 at 37$\circ$C was the same level at 30$\circ$C. However, the level of ADH activity of S. cerevisiae D at 37$\circ$C decreased about 70% of that at 30$\circ$C. The level of enzyme activity of K. marxianus RA-912, which showed lower alcohol productivity than S. cerevisiae RA-74-2 and D, was about 43% of those strains at 30$\circ$C, and decreased somewhat at 37$\circ$C. The results showed a good correlation between the alcohol productivities and the level of ADH activities of these strains grown at 30$\circ$C and 37$\circ$C. And the higher heat stability of ADH of S. cerevisiae RA-74-2 than that of S. cerevisiae D seemed to reflect the ability of high temperature fermentation. Despite of its fermentation ability even at 45$\circ$C, however, the ADH of K. marxianus RA-912 showed lower heat stability than that of S. cerevisiae D. Both S. cerevisiae RA-74-2 and D showed similar patterns of two bands of ADH isozyme, and the low band of S. cerevisiae RA-74-2 moved slightly faster than that of S. cerevisiae D. The staining intensity of the bands of S. cerevisiae D at 37$\circ$C was weaker than those at 30$\circ$C. However, S. cerevisiae RA-74-2 showed no differences in total intensity of the bands of 30$\circ$C and 37$\circ$C. As the patterns of cellular proteins and ADH isozyme of K. marxianus RA-912 were different from S. cerevisiae RA-74-2 and D, K. marxianus might have its own characteristic ADH system.