Sommer U, Spindler K D
Institut für Zoologie, Heinrich-Heine-Universität Düsseldorf, Federal Republic of Germany.
Arch Insect Biochem Physiol. 1991;18(1):45-53. doi: 10.1002/arch.940180105.
Kc-cells from Drosophila produce two different beta-D-hexosaminidases, a beta-N-acetyl-D-glucosaminidase (E.C.3.2.1.30) and a beta-N-acetyl-D-hexosaminidase (E.C.3.2.1.52), which are also secreted into the medium. The Mr of both enzymes is about 126,000 +/- 9,700; the S-values are 8.37 +/- 0.44. Both enzymes have about the same pH optima at 5.5 and the same thermal stability. The temperature optima are identical (50 degrees C) for both enzymes if p-nitrophenyl-N-acetylglucosaminide is used as a substrate. However, when p-nitrophenyl-N-acetylgalactosaminide is used as the substrate the beta-N-acetyl-D-hexosaminidase has a temperature optimum about 10 degrees C higher. With higher salt concentrations, the activity of the beta-N-acetyl-D-glucosaminidase increases, whereas beta-N-acetyl-D-hexosaminidase is inhibited. Both enzymes also differ in their sensitivity to urea, the beta-N-acetyl-D-hexosaminidase being less sensitive than the beta-N-acetyl-D-glucosaminidase.
果蝇的Kc细胞产生两种不同的β-D-己糖胺酶，一种是β-N-乙酰-D-葡糖胺酶（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），它们也分泌到培养基中。两种酶的相对分子质量约为126,000±9,700；沉降系数为8.37±0.44。两种酶在pH 5.5时具有大致相同的最适pH值和相同的热稳定性。如果使用对硝基苯基-N-乙酰葡糖胺作为底物，两种酶的最适温度相同（50℃）。然而，当使用对硝基苯基-N-乙酰半乳糖胺作为底物时，β-N-乙酰-D-己糖胺酶的最适温度约高10℃。在较高盐浓度下，β-N-乙酰-D-葡糖胺酶的活性增加，而β-N-乙酰-D-己糖胺酶受到抑制。两种酶对尿素的敏感性也不同，β-N-乙酰-D-己糖胺酶比对β-N-乙酰-D-葡糖胺酶的敏感性低。
