The enzyme from Thermoanaerobacter brockii can act with α-1,2-oligoglucans, such as selaginose, as substrate, but more slowly. The enzyme is inactive when dissaccharides with linkages other than α-1,2 linkages, such as sophorose, trehalose, neotrehalose, nigerose, laminaribiose, maltose, cellobiose, isomaltose, gentiobiose, sucrose and lactose, are used as substrates.