초록
The${\beta}$-glucosidases occur widely in all living organisms and has in general a tendency to form oligomers of varying numbers of subunits or aggregates, although the functional implications of such diverse oligomerization schemes remain unclear. In particular, the assembly mode of the oat ${\beta}$-glucosidase is very unique in that it multimerizes by linear stacking of a hexameric building block to form long fibrillar multimers. Some structural proteins such as actin and tubulin assemble into long fibrils in a helical fashion and several enzymes such as GroEL and Pyrodictium ATPase functional complexes, 20S proteasome of the archaebacterium Thermoplasma acidophilum, and lutamine synthetase fromblue-green algae, assemble into discrete oligomers upto 4 stacked rings to maintain their enzymatic activities. In particular, oat ${\beta}$-glucosidase exists in vivo as a discrete long fibrillar multimer assembly that is a novel structure for enzyme protein. It is assembled by linear stacking of hollow trimeric units. The fibril has a long central tunnel connecting to the outer medium via regularly distributed side fenestrations. The enzyme active sites are located within the central tunnel and multimerization increases enzyme affinity to the substrates and catalytic efficiency of the enzyme. Although it is suggested that oligomerization may contribute to the enzyme stability and catalytic efficiency of ${\beta}$-glycosidases, the functional implications of such diverse oligomerization schemes remain unclear so far.