Sommer U, Spindler K D
Institut für Zoologie, Heinrich-Heine-Universität Düsseldorf, F.R.G.
Arch Insect Biochem Physiol. 1991;17(1):3-13. doi: 10.1002/arch.940170103.
Kc-cells from Drosophila melanogaster, grown under serum-free conditions, produce two beta-hexosaminidases and secrete these enzymes into the medium. The two enzymes were separated by DEAE-exchange chromatography. According to their substrate specificities one enzyme is a beta-N-acetyl-D-glucosaminidase (E.C.3.2.1.30), the other one a beta-N-acetyl-D-hexosaminidase (E.C.3.2.1.52). The beta-N-acetyl-D-glucosaminidase is predominant in the medium, the beta-N-acetyl-D-hexosaminidase within the cells. The Km values for the substrates pNP-GlcNAc, pNP-GalNAc, and (GlcNAc)2 are 0.8, 16.73, and 1.67 mM for the beta-N-acetyl-D-glucosaminidase and 0.24, 0.44, and 0.2 mM for the beta-N-acetyl-D-hexosaminidase. Both enzymes are inhibited by the products and the beta-N-acetyl-D-glucosaminidase is also inhibited stereospecifically by the substrates pNP-GlcNAc and (GlcNAc)2. Both enzymes are inhibited in a partial competitive way by acetamidolactones, the Kis being as low as 0.1 microM.
在无血清条件下培养的黑腹果蝇Kc细胞可产生两种β-己糖胺酶，并将这些酶分泌到培养基中。这两种酶通过DEAE离子交换色谱法分离。根据它们的底物特异性，一种酶是β-N-乙酰-D-氨基葡萄糖苷酶（E.C.3.2.1.30），另一种是β-N-乙酰-D-己糖胺酶（E.C.3.2.1.52）。β-N-乙酰-D-氨基葡萄糖苷酶在培养基中占主导，β-N-乙酰-D-己糖胺酶在细胞内占主导。对于底物对硝基苯-N-乙酰-D-氨基葡萄糖（pNP-GlcNAc）、对硝基苯-N-乙酰-D-氨基半乳糖（pNP-GalNAc）和N,N'-二乙酰壳二糖（(GlcNAc)2），β-N-乙酰-D-氨基葡萄糖苷酶的米氏常数（Km值）分别为0.8、16.73和1.67 mM，β-N-乙酰-D-己糖胺酶的Km值分别为0.24、0.44和0.2 mM。两种酶均受产物抑制，β-N-乙酰-D-氨基葡萄糖苷酶还受到底物pNP-GlcNAc和(GlcNAc)2的立体特异性抑制。两种酶均受到乙酰胺内酯的部分竞争性抑制，抑制常数（Ki）低至0.1 μM。
