Cygan J, Neufeld-Kaiser W, Jara G, Daniel W L
Department of Cell and Structural Biology, University of Illinois, Urbana 61801, USA.
Comp Biochem Physiol B Biochem Mol Biol. 1997 Apr;116(4):437-46. doi: 10.1016/s0305-0491(96)00290-8.
Artiodactyls possess abundant neutral glycosidase activity in liver, kidney and intestine. This enzyme is cytosolic and displays a more neutral pH optimum, more acidic isoelectric point and broader substrate range than the corresponding acidic beta-galactosidases. The neutral glycosidases were more thermolabile than the respective acidic beta-galactosidases and displayed a relative molecular mass approximating 60 kDa. This isozyme appeared to be a minor species in both rat and dog liver. The porcine enzyme was studied in more detail. Porcine neutral glycosidase activity was detected in 45-day gestational fetuses in both liver and kidney but not brain. Fetal kidney activities were about half those observed in adult kidney extracts. Porcine neutral glycosidase was immunologically distinct from acidic beta-galactosidase and was immunologically similar to the corresponding isozymes from deer, ovine and bovine liver. Porcine neutral glycosidase was moderately inhibited by D-galactonic acid gamma-lactone and strongly inhibited by D-gluconic acid delta-lactone; however, acidic beta-galactosidase was not inhibited by the delta-lactone. Inhibition by the gamma-lactone was competitive for both enzymes. 4-Methylumbelliferyl-beta-D-galactoside,-glucoside and -xyloside competed for the same active site. A polymorphism for fast- and slow-migrating isozymes of porcine neutral glycosidase was observed, which appeared to be under genetic control.
偶蹄目动物的肝脏、肾脏和肠道中存在丰富的中性糖苷酶活性。这种酶存在于胞质中，与相应的酸性β-半乳糖苷酶相比，其最适pH更接近中性，等电点更偏酸性，底物范围更广。中性糖苷酶比相应的酸性β-半乳糖苷酶更不耐热，相对分子质量约为60 kDa。这种同工酶在大鼠和狗的肝脏中似乎都是次要类型。对猪的这种酶进行了更详细的研究。在妊娠45天的胎儿肝脏和肾脏中检测到了猪中性糖苷酶活性，但在大脑中未检测到。胎儿肾脏中的活性约为成年肾脏提取物中观察到的活性的一半。猪中性糖苷酶在免疫上与酸性β-半乳糖苷酶不同，在免疫上与鹿、羊和牛肝脏中的相应同工酶相似。猪中性糖苷酶受到D-半乳糖酸γ-内酯的中度抑制，受到D-葡萄糖酸δ-内酯的强烈抑制；然而，酸性β-半乳糖苷酶不受δ-内酯的抑制。γ-内酯对这两种酶的抑制作用都是竞争性的。4-甲基伞形酮基-β-D-半乳糖苷、-葡萄糖苷和-木糖苷竞争相同的活性位点。观察到猪中性糖苷酶快速迁移和慢速迁移同工酶的多态性，这似乎受遗传控制。
