The GtfD enzyme of Azotobacter chroococcum is a unique evolutionary intermediate between glycoside hydrolase family GH13 (α-amylase) and GH70 (glucansucrase). The product of GtfD is a high molecular mass α(1→4,6) branched reuteran like polymer with 68 % α(1→4), and 32 % α(1→6) glycosidic linkages using amylose V as substrate. The polymer has a molecular weight of 13 MDa. The glucan is highly similar to the product formed by Lactobacillus reuteri GtfA glucansucrase from sucrose.