The biochemistry of rumen protozoa. 2. Some carbohydrases in cell-free extracts of Dasytricha and Isotricha

Abstract

Cell-free extracts, nearly free from bacteria, have been prepared from suspensions of the 2 genera of rumen holotrich Protozoa, Dasytricha and Isotricha. The ability of these extracts to split a number of di-, tri- and poly-saccharides has been investigated. Hydrolytic activity of the extracts corresponded to the ability of the living Protozoa to ferment the substrates. Dasytricha ruminantium extracts contained appreciable cellobiase and [beta]-glucosidase activity, and moderate maltase activity. Extracts of mixed Isotricha intestinalis and I. prostoma contained hardly any maltase, a trace of cellobiase and a small amount of [beta]-glucosidase. Neither genus gave extracts able to hydrolyze lactose, melibiose, trehalose, melezitose or zylobiose. Considerable invertase activity was found in the protozoal extracts, especially those from Isotricha. Sucrose, raffinose, inulin and a bacterial levan were all hydrolyzed, but not melezitose. The transferring activity of the invertase was examined, and some products of transfructosylation were isolated and identified. The protozoal invertase resembles most closely that of yeast.