methods4-Methylumbelliferyl-N-acetyl-d-glucosaminide [4MU-(GlcNAc)], 4MU-(GlcNAc)2, 4MU-(GlcNAc)3, and -chitin fromshrimp shells were purchased from Sigma-Aldrich (St. Louis, MO,USA). -Chitin from squid pen was purchased from Seikagaku(Tokyo, Japan).