THE CELL-BOUND α-AMYLASES OF STREPTOCOCCUS BOVIS

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Abstract
The cell-bound [alpha]-amylase of S. bovis has been isolated from other carbohydrases in the cell extract by chromatography on diethylaminoethyl (DEA) cellulose. The enzyme has been compared with the extracellular a-amylase produced by this organism. The two amylases had similar action patterns on amylose the main product being maltotriose with smaller amounts of maltose and a little glucose. The cell bound amylase hydrolyzed maltopentaose and maltohexaose at a similar rate to the hydrolysis of amylose. Malto-tetraose was hydrolyzed six times more slowly, and maltotriose 280 times more slowly, than amylose. Studies with end-labelled maltodextrins revealed that the cell-bound a-amylase preferentially hydrolyzed the third linkage from the non-reducing end, liberating maltotriose. The linkage at the reducing end of maltotriose was more easily hydrolyzed than the other. Egg-white lysozyme and the extracellular enzymes of S. albus lysed the cell walls of S. bovis, releasing amylase into the medium. In the presence of 0[center dot]6 M-sucrose 10% of the maximal amylase activity was released by lysozyme. Suspension of the spheroplasts in dilute buffer caused the rupture of the cytoplasmic membrane and the liberation of amylase. A sensitive method for determining the ability of amylases to degrade starch granules is described.