Purification and properties of endo-beta-N-acetylglucosaminidase L from Streptomyces plicatus.

An enzyme, previously described as endo-beta-N-acetylglucosaminidase L (Tarentino, A.L., and Maley, F. (1974) J. Biol. Chem. 249, 811-817) because of its apparent specificity for Man(GlcNAc)2Asn, has been purified to homogeneity. The enzyme has now been found to hydrolyze (GlcNAc)3 to (GlcNAc)2 plus GlcNAc, and (GlcNAc)4 to 2(GlcNAc)2, at twice the rate observed for Man(GlcNAc)2Asn. Removal of the asparagine from the latter compound reduces the rate of hydrolysis by about 30-fold. Reduction of (GlcNAc)3 to GlcNAc beta 1 leads to 4GlcNAc beta 1 leads to 4GlcNAc-ol eliminates this compound as a substrate for endo-beta-N-acetylglucosaminidase L. However, the reduction of (GlcNAc)4 does not affect its rate of hydrolysis. Endo-beta-N-acetylglucosaminidase L consists of a single polypeptide chain with a molecular weight of 49,500 +/- 400, which on isoelectric focusing separates into two closely migrating bands; a major with a pI of 4.25 and a minor one with a pI 4.20. Both bands possess similar enzyme activities and amino acid compositions, but differ slightly in their tryptic peptide maps.