The Degradation of Polygalacturonic Acid by Rumen Ciliate Protozoa

Biochemistry Department, Agricultural Research Council, Institute of Animal Physiology, Babraham, Cambridge CB 2 4 AT ABSTRACT Summary: The depolymerase activity of cell-free extracts of nine species of rumen ciliate protozoa and two mixed protozoal preparations, grown in vivo and in vitro , towards polygalacturonic acid was examined. The highest activity was found with Eremoplastron bovis and Ostracodinium obtusum bilobum while there was none in the spined or spineless forms of Entodinium caudatum and little in Polyplastron multivesiculatum. On the basis of the rapid drop in viscosity, inhibition by EDTA and the production of u.v.-absorbing material, the enzymes from all active species were designated as endopectate lyases (EC 4.2.2.2 ) although some polygalacturonase may be present. Neither pectin nor polygalacturonic acid supported the survival or growth of any of the protozoal species tested.