ChiA showed very high catalytic activity, even at 4◦C, and exhibited maximal activity on a chitin-ous substrate at pH 8.0 and 20◦C. Kinetic studies indicated that ChiA has a greater catalytic efficiency on4-methylumbelliferyl--d-N,N,N-triacetylchitotriose[4-MU(GlcNAc)3] than on 4-methylumbelliferyl--d-N,N-diacetylchitobioside[4-MU(GlcNAc)2].