Izumi T, Suzuki K
Biochim Biophys Acta. 1980 Oct;615(2):402-13. doi: 10.1016/0005-2744(80)90507-0.
The bulk of rat brain neutral beta-N-acetylhexosaminidases (2-acetamido-2-deoxy-beta-D-hexoside acetamidodeoxyhexohydrolase, EC 3.2.1.52) were present in the cytosol fraction. They were not bound by concanavalin A-Sepharose while the acid beta-N-acetylhexosaminidases were all bound. The neutral beta-N-acetylgalactosaminidase had a pH optimum of 5.2 and Km of 0.57 mM, while the neutral beta-N-acetylgalactosaminidase had the highest reaction rate at lost more than 90% of the activity in 30 min at 50 degrees C. The galactosaminidase pH 6.0 with a Km of 0.12 mM. No divalent ions activated either of the enzymes. The galactosaminidase was heat-stable and lost only 10--20% of its activity after 3 h at 50 degrees C. The neutral glucosaminidase was inhibited by free N-acetylglucosamine but not by N-acetylgalactosamine. The reverse was found for the neutral beta-galactosaminidase. Two enzymes were separated almost completely by hydroxyapatite chromatography. Heat stability of the separated activity peaks suggested that the neutral beta-N-acetylgalactosaminidase, which was not bound to hydroxyapatite, may be specific to the galactosaminide substrate. The neutral beta-N-acetylglucosaminidase may, on the other hand, have some activity toward the galactosaminide substrate. Both of the neutral enzyme activities were highest during the first postnatal week in rat brain in contrast to the acidic enzyme which showed peak activities during the second and third weeks. These results confirmed and expanded earlier observations by Frohwein and Gatt in calf brain. The relationship of these enzymes to the hexosaminidase C in human tissues is less certain at the present time.
大鼠脑中性β-N-乙酰己糖胺酶（2-乙酰氨基-2-脱氧-β-D-己糖苷乙酰氨基脱氧己糖水解酶，EC 3.2.1.52）大部分存在于胞质溶胶部分。它们不与伴刀豆球蛋白A-琼脂糖结合，而酸性β-N-乙酰己糖胺酶则全部结合。中性β-N-乙酰半乳糖胺酶的最适pH为5.2，Km为0.57 mM，而中性β-N-乙酰半乳糖胺酶在50℃下30分钟内活性损失超过90%时反应速率最高。半乳糖胺酶的pH为6.0，Km为0.12 mM。没有二价离子激活这两种酶中的任何一种。半乳糖胺酶热稳定，在50℃下3小时后仅损失10%-20%的活性。中性葡糖胺酶被游离N-乙酰葡糖胺抑制，但不被N-乙酰半乳糖胺抑制。中性β-半乳糖胺酶的情况则相反。两种酶通过羟基磷灰石层析几乎完全分离。分离活性峰的热稳定性表明，不与羟基磷灰石结合的中性β-N-乙酰半乳糖胺酶可能对半乳糖胺底物具有特异性。另一方面，中性β-N-乙酰葡糖胺酶可能对半乳糖胺底物有一些活性。与在出生后第二和第三周显示活性峰值的酸性酶相反，两种中性酶活性在大鼠脑出生后的第一周最高。这些结果证实并扩展了Frohwein和Gatt早期在小牛脑中的观察结果。目前这些酶与人体组织中己糖胺酶C的关系尚不太明确。
