The enzyme from?Streptomyces?specifically hydrolyses the terminal lacto-N-biosyl residue (¦Â-D-Gal-(1¡ú3)-D-GlcNAc) from the non-reducing end of oligosaccharides with the structure ¦Â-D-Gal-(1¡ú3)-¦Â-D-GlcNAc-(1¡ú3)-¦Â-D-Gal-(1¡úR). Lacto-N-hexaose (¦Â-D-Gal-(1¡ú3)-¦Â-D-GlcNAc-(1¡ú3)-¦Â-D-Gal-(1¡ú3)-¦Â-D-GlcNAc-(1¡ú3)-¦Â-D-Gal-(1¡ú4)-D-Glc) is hydrolysed to form first lacto-N-tetraose plus lacto-N-biose, with the subsequent formation of lactose. Oligosaccharides in which the non-reducing terminal Gal or the penultimate GlcNAc are replaced by fucose or sialic acid are not substrates. Asialo GM1 tetraose (¦Â-D-Gal-(1¡ú3)-¦Â-D-GalNAc-(1¡ú3)-¦Â-D-Gal-(1¡ú4)-D-Glc) is hydrolysed very slowly, but lacto-N-neotetraose (¦Â-D-Gal-(1¡ú4)-¦Â-D-GalNAc-(1¡ú3)-¦Â-D-Gal-(1¡ú4)-D-Glc) is not a substrate.