Starch-debranching enzyme involved in amylopectin biosynthesis in endosperm. Functions by removing excess branches or improper branches that interfere with the formation of double helices of the cluster chains of amylopectin and crystallization of starch (PubMed:16953433, PubMed:21436381). Works together with ISA1 as heterooligomer. The heterooligomer ISA1 and ISA2 possesses higher affinity than the ISA1 homooligomer for various branched polyglucans in vitro, but no marked differences exist in chain preferences for debranching of amylopectin and phytoglycogen between these forms (PubMed:16953433, PubMed:21436381). Hydrolysis of (1->6)-alpha-D-glucosidic branch linkages in glycogen, amylopectin and their beta-limit dextrins. Forms a hetero-hexamer composed of five ISA1 and one ISA2. Highly expressed in developing endosperm and leaves. Belongs to the glycosyl hydrolase 13 family. Truncated N-terminus. Truncated N-terminus. Truncated N-terminus.