One of the isoamylase isoforms, CMI294C, is required for semi-amylopectin synthesis in the rhodophyte .

Most rhodophytes synthesize semi-amylopectin as a storage polysaccharide, whereas some species in the most primitive class (Cyanidiophyceae) make glycogen. To know the roles of isoamylases in semi-amylopectin synthesis, we investigated the effects of gene ( and )-deficiencies on semi-amylopectin molecular structure and starch granule morphology in (Cyanidiophyceae). Semi-amylopectin content in a -disruption mutant () was not significantly different from that in the control strain, while that in a -disruption mutant () was much lower than those in the control strain, suggesting that CMI294C is essential for semi-amylopectin synthesis.