ELECTRON-MICROSCOPIC INVESTIGATION OF THE DIFFUSION OF BACILLUS-LICHENIFORMIS ALPHA-AMYLASE INTO CORN STARCH GRANULES

A method for the direct electron microscopic observation of amylases i n interaction with starch granules is presented. The technique involve s immune-gold labeling of the enzymes and cross-sectioning of hydrated starch granules. This approach allows the analysis of the internal de gradation of starch with a concomitant visualization of enzymes at the sites of hydrolysis. The visualization of enzymes at the surface, ins ide the channel and inside the core of the degraded granules shows tha t the cc-amylase molecules first proceed from the surface toward the c enter (centripetal hydrolysis). Then the core is completely degraded f rom within by erosion of its periphery (centrifugal hydrolysis), In th e first case (centripetal hydrolysis), the enzymes act by progressing along the polysaccharide chains. By contrast, the centrifugal hydrolys is leads to even erosion, indicative of a more diffusive motion of the enzymes.