Activation and Cell-Surface Localization of Certain β-Glucosidases of the Ruminal Flora

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Abstract
Kinetic and inhibition studies of the cellulases in crude extracts of ruminal ingesta indicated the participation of sulfhydryl groups and polyvalent metal ions in enzymic hydrolysis of cellulose. As a result, the assay substrate has been modified by inclusion of ferric chloride. A minimum estimate was obtained of the proportion of the cellulolytic activity in ruminal ingesta which is intimately associated with bacterial cell surfaces. A series of fractionations employing washing of the bacterial cells by centrifugation, rupture in a French pressure cell, and lysis using desoxycholate yielded an estimate of 5%. Reasons for suspecting that surface-bound cellulases may occur in considerably larger proportions were discussed.