脂蛋白脂肪酶是采用筛选得到的细菌菌株,经独特发酵工艺制备的脂蛋白脂肪酶制剂。
来源:伯克霍尔德菌(Burkholderia sp.,旧称假单胞菌 Pseudomonas sp.)
催化反应:甘油三酯 + 3H₂O → 甘油 + 3RCOOH
规格
酶活:≥1000 U/mg 酶粉
外观:白色冻干粉
杂质:不含氧化酶
添加剂:甘氨酸
特性
1. 分子量:33 000(凝胶过滤法)
2. 等电点:4.3
3. Km:3.95×10⁻³ M
4. 最适 pH:7.0
5. pH 稳定性:5.0‑9.0(30 ℃,24 小时)
6. 最适温度:50 ℃
7. 热稳定性:最高 40 ℃(pH 7.0,30 min)
8. 抑制剂:胆酸钠
9. 稳定剂:Ca²⁺
10. 应用:临床诊断中,与相关酶偶联,用于血清甘油三酯的酶法测定。
安全操作注意事项
1. 请勿吸入本品。
2. 若皮肤或眼睛直接接触,立即用大量清水冲洗。
一般性质
下述结果为不同缓冲液配制的酶溶液活性数据。
酶活性会随实验条件不同发生变化。
脂蛋白脂肪酶活性测定方法
测定原理
本测定基于对上述反应释放出的脂肪酸进行滴定。
单位定义
一个酶活单位定义为:在下文所述测定条件下,每分钟释放 1 μmol 脂肪酸所需的酶量。
试剂
A. 2/15 M 磷酸盐缓冲液(KH₂PO₄‑Na₂HPO₄,pH 7.0)
B. 1/15 M 磷酸盐缓冲液(KH₂PO₄‑Na₂HPO₄,pH 7.0)
C. 底物溶液
称取 1.60 g 牛血清白蛋白(V 组分),溶于 16 mL 2/15 M 磷酸盐缓冲液(A)。向该溶液加入 24 mL 10% 英脱利匹特(大豆油),充分搅拌。(冷藏条件下仅可现配现用)
D. 庚烷‑2‑丙醇‑硫酸溶液
依次混合 75 mL 庚烷、300 mL 2‑丙醇、7.5 mL 1 mol/L 硫酸。(室温可保存 3 个月)
E. 甲酚红指示剂
称取 50 mg 甲酚红,溶于 50 mL 乙醇,滤纸过滤。(室温棕色瓶或冷藏可保存 1 个月)
F. Triton X‑100 储备液(5 g/100 mL 去离子水)
G. 稀释液
取约 900 mL 1/15 M 磷酸盐缓冲液(B),加入 2 mL Triton X‑100 储备液(F),用 1/15 M 磷酸盐缓冲液(B)定容至 1000 mL。
H. 酶溶液
称取脂蛋白脂肪酶,用预冷稀释液(G)温和溶解。
配制酶溶液时,应使 (T20‑T0) 数值落在 0.25‑0.50 mL 区间。
禁止剧烈振荡酶溶液,否则会造成酶失活。
I. 0.01 N 氢氧化钾‑乙醇溶液
移取 5 mL 0.1 mol/L 氢氧化钾乙醇溶液(市售滴定分析用)置于 50 mL 容量瓶,用乙醇定容至 50 mL。
操作步骤
向带磨口塞试管(Φ25×200 mm)中分别移入 1.0 mL 2/15 M 磷酸盐缓冲液(A)、2.0 mL 底物溶液(C),混匀。置于 37±0.5 ℃水浴摇床保温 10 min 以上,加入 1.0 mL 酶溶液(H),振荡孵育。
加入酶溶液(H)精确计时 20 min 后,加入 10.0 mL 庚烷‑2‑丙醇‑硫酸溶液(D)充分振荡混匀;再加入 6.0 mL 庚烷与 4.0 mL 去离子水,盖紧瓶塞摇振 5 min。
摇振结束后,试管置于自来水中静置 20 min 以上,使庚烷相与水相分层。
吸取 6.0 mL 上层庚烷相至试管(Φ15×105 mm),滴加 2 滴甲酚红指示剂(E)。氮气保护搅拌条件下,使用 0.01 N 氢氧化钾‑乙醇溶液(I)滴定,记录体积 T20 mL;溶液变为紫罗兰色即为滴定终点。
空白对照:取另一支带磨口塞试管(Φ25×200 mm),移入 1.0 mL 2/15 M 磷酸盐缓冲液(A)与 2.0 mL 底物溶液(C),加入 10.0 mL 庚烷‑2‑丙醇‑硫酸溶液(D)混匀,再加 1 mL 酶溶液(H),按上述完全相同流程操作,记录体积 T0 mL。
计算
20:反应时间
10:换算因子(1 mL 0.01 N 氢氧化钾‑乙醇溶液相当于 10 μmol 脂肪酸)
1.327:庚烷总体积 / 取用庚烷体积 = (6+10/51×10) / 6 = 1.327
f:0.01 N 氢氧化钾‑乙醇溶液当量系数
n:酶溶液稀释倍数
Lipoprotein Lipase is a lipoprotein lipase preparation manufactured by a unique fermentation process using a selected strain of bacteria.
ORIGIN : Burkholderia sp. (formerly Pseudomonas sp.)
CATALYSIS : Triglyceride + 3H₂O → Glycerol + 3RCOOH
Specification:
Activity: ≥1000 U/mg enzyme powder
Appearance: White powder, lyophilized
Contaminants: Oxidase free
Additives: Glycine
Characteristics:
1. Molecular weight: 33,000 (Gel filtration)
2. Isoelectric point: 4.3
3. Km: 3.95×10⁻³ M
4. Optimum pH: 7.0
5. pH stability: 5.0‑9.0 (30 °C, 24hrs)
6. Optimum temperature: 50 °C
7. Thermal stability: up to 40 °C (pH 7.0, 30 min)
8. Inhibitor: Sodium Cholate
9. Stabilizer: Ca²⁺
10. Application: Used for the enzymatic determination of triglyceride in serum by coupling with the related enzymes in clinical diagnosis.
Safe Handling:
1. Do not inhale.
2. In case of direct contact with skin or eyes, immediately wash or rinse with plenty of water.
General properties
The following results demonstrate the activities of enzyme solution prepared in various buffers.
Enzyme activity may vary under different experimental conditions.
Assay method of Lipoprotein lipase activity
Principle
The assay is based on the titration of fatty acid liberated from the above reaction.
Unit Definition
One unit is defined as the enzyme quantity which liberates one μ mole of fatty acid per minute under the conditions described below.
Reagents
A. 2/15 M Phosphate buffer (KH₂PO₄‑Na₂HPO₄, pH7.0)
B. 1/15 M Phosphate buffer (KH₂PO₄‑Na₂HPO₄, pH 7.0)
C. Substrate solution
Weigh 1.60 g of bovine serum albumin (Fraction V) and dissolve in 16 ml of 2/15 M Phosphate buffer (A). Add 24 ml of 10% Intralipos (soybean oil) into the solution and stir well. (Can be used only on the day of preparation if refrigerated)
D. Heptane‑2‑propanol‑sulfuric acid solution
Mix 75ml of heptane, 300 ml of 2‑propanol, and 7.5 ml of 1 mol/L sulfuric acid successively. (Can be used for 3 months at room temperature)
E. Cresol red indicator
Weigh 50 mg of cresol red and dissolve in 50 ml of ethanol. Filtrate with filter paper. (Can be used for 1 month if stored in a brown bottle at room temperature or in a refrigerator)
F. Triton X‑100 stock solution (5g/100ml deionized water)
G. Diluent
Mix approx. 900ml of 1/15 M Phosphate buffer (B) and 2 ml of Triton X‑100 stock solution (F), then fill up to 1000 ml with 1/15 M Phosphate buffer (B).
H. Enzyme solution
Weigh out Lipoprotein Lipase and gently dissolve in chilled Diluent (G).
Enzyme solution should be prepared so that the value of (T20‑T0) becomes in the range of 0.25 − 0.50 ml.
Do not shake the Enzyme solution vigorously, or the enzyme becomes inactive.
I. 0.01N KOH‑ethanol solution
Pipette 5 ml of 0.1 mol/L potassium hydroxide ethanolic solution (Commercial product, for volumetric analysis) into a volumetric flask (50 ml) and fill up to 50 ml with ethanol.
Procedure
Pipette 1.0 ml of 2/15M Phosphate buffer (A) and 2.0 ml of Substrate solution (C) respectively into a test tube (Φ25 × 200 mm) with a ground stopper and mix well. Stand the solution in a water bath shaker at 37 ± 0.5 °C for more than 10 minutes, then add 1.0 ml of Enzyme solution (H) and incubate with shaking.
Exactly 20 minutes after addition of Enzyme solution (H), add 10.0 ml of Heptane‑2‑propanol‑sulfuric acid solution (D), then shake and mix well. Add 6.0 ml of heptane and 4.0 ml of deionized water, then cap the stopper and shake using shaker for 5 minutes.
After shaking, stand the reaction mixture in tap water for more than 20 minutes to make heptane layer separate from water layer.
Pipette 6.0 ml of upper layer (heptane layer) into a test tube (Φ15 × 105 mm) and add 2 drops of Cresol red indicator (E). Then, titrate the solution with 0.01N KOH‑ethanol solution (I) in nitrogen currents while stirring (T20 ml). It is the end point that the color of the solution turns violet.
As a blank, pipette 1.0 ml of 2/15 M Phosphate buffer (A) and 2.0 ml of Substrate solution (C) into another test tube (Φ25 × 200 mm) with ground stopper, then add 10.0 ml of Heptane‑2‑propanol‑sulfic acid solution (D) and mix well. Add 1 ml of Enzyme solution (H) and take the same procedure described above (T0 ml)
Calculation
20: Reaction time
10: Conversion factor (1 ml of 0.01N KOH‑ethanol solution corresponds to 10 μ moles of fatty acid)
1.327: Total heptane / 6 ml of heptane = (6+10/51×10) / 6 = 1.327
f: Normality coefficient of 0.01N KOH‑ethanol solution
n: Dilution factor of Enzyme solution