Genetic and Biochemical Studies on Cell-Bound α-Amylase in Bacillus subtilis Marburg

Abstract

A small but significant amount of α-amylase activity was detected in the cells of Bacillus subtilis Marburg. The cell-associated activity was almost constant regardless of the level of extracellular α-amylase activity. The cell-bound amylase activity could be separated into three components, upon Sephadex G-75 chromatography, referred to as components A, B, and C. Component C showed the same properties as the extracellular α-amylases so far examined. Component A had a molecular weight greater than 70,000, as judged from the elution position on Sephadex G-75, and became smaller upon treatment with trypsin but was still larger than that of component C. An α-amylase mutant that lacked extracellular α-amylase completely because of a mutation within the structural gene of the enzyme was found to lose all three cell-bound amylase components simultaneously. These data suggest strongly that the cell-bound amylase components are precursors of the extracellular α-amylase and that the α-amylase of this organism is produced under the direction of the same gene whether the enzyme is within or outside the cell.