An exopectate lyase of Butyrivibrio fibrisolvens from the bovine rumen

An extracellular pectinolytic enzyme produced by Butyrivibrio fibrisolvens isolated from the bovine rumen was studied. The enzyme had a pH optimum of 8.0 to 8.5 and was stimulated by Ca2+ and inhibited by EDTA. The products of pectinolysis had an absorption peak at 235 nm and reacted with thiobarbituric acid, indicating a lyase type of action. The enzyme cleaved the substrates terminally from the reducing end; action on poly- and oligogalacturonates resulted in the formation of an unsaturated trigalacturonate. The enzyme was classified as an exopectate lyase (EC 4.2.2.9). A pectinesterase was also produced by B. fibrisolvens but polygalacturonase was not detected.