Hydrolyzes the N-acetamido groups of N-acetyl-D-glucosamine residues in chitin. [(1->4)-N-acetyl-beta-D-glucosaminyl](n) + n H2O = n acetate + chitosan Binding to the accessory protein CPAP3-A1 is essential for chitinase activity. Interacts with CPAP3-A1. Highly expressed in epidermis and head. Moderate expression levels in fat body, Malpighian tubule, testis and midgut. Low expression in silk gland and ovary. Shows highest expression during pupal stages, with a peak during pupal day 1. Has relatively low expresson during larval development. Up-regulated in response to 20-hydroxyecdysone (20E) and juvenile hormone analog. Also up-regulated in response to the transcription factors BRC-Z2 and POUM2. RNAi-mediated knockdown results in delayed pupation. Belongs to the carbohydrate esterase 4 (CE4) family. Has no detectable chitin esterase activity in purified form. Enzymatic activity is detected in the presence of CPAP3-A1, or B.mori molting fluid. However, it is unclear whether this protein functions as a chitin esterase in vivo.