Cavanagh K, Dunstan R W, Jones M Z
Am J Vet Res. 1983 Apr;44(4):681-4.
Experimental conditions for measuring caprine plasma beta-D-mannosidase activity are described with p-nitrophenyl-beta-D-mannopyranoside as a substrate. The plasma enzyme was stable for 3 months at -20 C or 1 week at 4 C. The optimal pH for activity was 5.0 in citrate-phosphate or acetate buffer. Enzyme activity was linear with time up to 24 hours at 37 C, but incubation of plasma at 56 C for 5 minutes resulted in loss of all activity. The apparent Michaelis-Menten constant (Km) for the plasma enzyme was 10.0 mM. Plasma beta-mannosidase from clinically normal and beta-mannosidosis carrier goats did not differ with respect to pH optimum, heat stability, or Km. The coefficient of variation for the assay, determined by assaying a plasma pool over a 3-month period, was 10.7% (mean: 115 nmole of p-nitrophenol formed/hour/ml of plasma). The assay described can be used to evaluate plasma beta-mannosidase measurements as a test for detecting carriers of caprine beta-mannosidosis, a newly described lysosomal storage disease.
描述了以对硝基苯基-β-D-甘露吡喃糖苷为底物测量山羊血浆β-D-甘露糖苷酶活性的实验条件。血浆酶在-20℃下可稳定保存3个月，在4℃下可稳定保存1周。在柠檬酸盐-磷酸盐或乙酸盐缓冲液中，酶活性的最适pH为5.0。在37℃下，酶活性与时间呈线性关系，长达24小时，但血浆在56℃下孵育5分钟会导致所有活性丧失。血浆酶的表观米氏常数（Km）为10.0 mM。临床正常山羊和β-甘露糖苷贮积症携带者山羊的血浆β-甘露糖苷酶在最适pH、热稳定性或Km方面没有差异。通过在3个月内对血浆样本进行检测，该检测方法的变异系数为10.7%（平均值：每小时每毫升血浆形成115纳摩尔对硝基苯酚）。所描述的检测方法可用于评估血浆β-甘露糖苷酶测量结果，作为检测山羊β-甘露糖苷贮积症携带者的一项检测，β-甘露糖苷贮积症是一种新描述的溶酶体贮积病。
