PHOSPHOENOLPYRUVATE CARBOXYLASE from Microorganism
Appearance | White amorphous powder, lyophilized | |
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Activity | GradeⅢ 5.0 U/mg-solid or more | |
Contaminants | Lactate dehydrogenase | ≤ 1.0×10-3 % |
Pyruvate kinase | ≤ 0.05% | |
Stabilizers | BSA, sugar alcohols |
Stability | Stable at −20 ℃ for at least one year (Fig.1) |
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Molecular weight | approx. 390,000 (by gel filtration) |
Isoelectric point | 6.0±0.1 |
Structure | 4 Subunits (M.W.100,000) per enzyme molecule |
Michaelis constant | 1.9×10-4 M (Phosphoenolpyruvate) |
Optimum pH | 7.5−8.0 (Fig.2) |
Optimum temperature | 60 ℃ (Fig.3) |
pH Stability | pH 5.0−8.0 (25 ℃, 24 hr) (Fig.4) |
Thermal stability | below 40 ℃ (pH 7.0, 15 min) (Fig.5) |
This enzyme is useful for enzymatic determination of carbon dioxide in combination with malate dehydrogenase (MAD-211) in clinical analysis.
The formation of NADH is measured at 340 nm by spectrophotometry.
One unit causes the oxidation of one micromole of NADH per minute under the conditions detailed below.
A. Buffer solution | 0.1 M Tris-HCl Buffer, pH 8.0 |
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B. Na2CO3 solution | 0.1 M[Dissolve 1.06 g of Na22CO3(MW=105.99)/100 mL of H2O] |
C. K-Phosphoenolpyruvate solution | 32 mM[Dissolve 33.0 mg of PEP・K(MW=206.1)/5 mL of H2O](Should be prepared fresh) |
D. MgSO4 solution | 1 M[Dissolve 4.93 g of MgSO4・7H2O(MW=246.48)/20 mL of H2O] |
E. NADH solution | 1.4 mM[Dissolve 5.34 mg of NADH・3H2O(MW=763)/5 mL of H2O] |
F. MDH solution | ca.100 U/mL[Dissolve malate dehydrogenase (TOYOBO GradeⅡ) to approx.100 U/mL with 20 mM Tris-HCl Buffer,pH 8.0](Should be prepared fresh) |
G. Enzyme diluent | 20 mM K-phosphate buffer, pH 7.0 |
1.Prepare the following reaction mixture in a cuvette (d = 1.0 cm) and equilibrate at 30 ℃ for approximately 5 minutes.
1.77 mL | Buffer solution | (A) |
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0.3 mL | Na2CO3 solution | (B) |
0.3 mL | Potassium phosphoenolpyruvate solution | (C) |
0.03mL | MgSO4 solution | (D) |
0.3 mL | NADH solution | (E) |
0.3 mL | MDH solution | (F) |
Concentration in assay mixture | |
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Potassium phosphoenolpyruvate | 3.1 mM |
Tris-HCl | 57 mM |
Na2CO3 | 9.7 mM |
MgSO4 | 9.7 mM |
NADH | 0.14 mM |
MDH | 9.7 U/mL |
Potassium phosphate | 0.65 mM |
2.Add 0.1 mL of the enzyme solution* and mix by gentle inversion.
3.Record the decrease in optical density at 340 nm against water for 3 to 4 minutes with a spectrophotometer thermostated at 30 ℃, and calculate the ΔOD per minute from the initial linear portion of the curve (ΔOD test).
At the same time, measure the blank rate (ΔOD blank) using the same method as in the test except that the enzyme diluent (G) is added instead of the enzyme solution.
*Dissolve the enzyme preparation in ice-cold enzyme diluent (G) and dilute to 0.2−0.7 U/mL with the same buffer and store on ice.
Activity can be calculated by using the following formula :
Volume activity (U/mL) =
ΔOD/min (ΔOD test−ΔOD blank)×Vt×df
6.22×1.0×Vs
= ΔOD/min×4.98×df
Weight activity (U/mg) = (U/mL)×1/C
Vt | : Total volume (3.1 mL) |
Vs | : Sample volume (0.1 mL) |
6.22 | : Millimolar extinction coefficient of NADH (cm2/micromole) |
1.0 | : Light path length (cm) |
df | : Dilution factor |
C | : Enzyme concentration in dissolution (c mg/mL) |
1) W.Wilson, P.Jesyk, R.Rand and R.D.Bevill; Clin.Chem.,19, 640(1973)
2) R.L.Forrester, L.J.Wataji, D.A.Silverman and K.J.Pierre; Clin.Chem.,22, 243(1976)
[The enzyme solution dissolved in 20 mM K-phosphate buffer, pH 7.0 (20 U/mL) was incubated with each chemical at 25 ℃ for 1 hr.]
Chemical | Concn.(mM) | Residual activity(%) |
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None | - | 100 |
Metal salt | 2.0 | |
MgCl2 | 105 | |
CaCl2 | 105 | |
Ba(OAc)2 | 103 | |
FeCl3 | 92 | |
CoCl2 | 106 | |
MnCl2 | 107 | |
ZnSO4 | 103 | |
Cd(OAc)2 | 104 | |
NiCl2 | 0 | |
CuSO4 | 0 | |
Pb(OAc)2 | 105 | |
AgNO3 | 0 | |
HgCl2 | 0 | |
MIA | 2.0 | 60 |
2-Mercaptoethanol | 2.0 | 101 |
Chemical | Concn.(mM) | Residual activity(%) |
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PCMB | 0.1 | 80 |
NEM | 2.0 | 87 |
IAA | 2.0 | 90 |
Hydroxylamine | 2.0 | 95 |
EDTA | 5.0 | 100 |
o-Phenanthroline | 2.0 | 103 |
α,α′-Dipyridyl | 2.0 | 109 |
Borate | 5.0 | 103 |
NaF | 2.0 | 106 |
NaN3 | 2.0 | 106 |
Triton X-100 | 0.10 % | 111 |
Brij 35 | 0.10 % | 110 |
Tween 20 | 0.10 % | 112 |
Span 20 | 0.10 % | 109 |
Na-cholate | 0.10 % | 108 |
SDS | 0.05 % | 1 |
DAC | 0.05 % | 99 |
Ac, CH3CO; PCMB, p-Chloromercuribenzoate; MIA, Monoiodoacetate; EDTA, Ethylenediaminetetraacetate; IAA, Iodoacetamide; NEM, N-Ethylmaleimide; SDS, Sodium dodecyl sulfate; DAC, Dimethylbenzylallkylammonium chloride.
Fig.1. Stability (Powder form)
(kept under dry conditions)
Fig.2. pH-Activity
30 ℃, in 50 mM buffer solution: pH 6.0-8.5, MES: pH 7.5-9.0, Tris-HCI
Fig.3. Temperature activity
(in 20 mM K-phosphate buffer,pH 7.0)
Fig.4. pH-Stability
25 ℃, 24 hr-treatment with 50mM buffer solution contg. 10 mM MgSO4: pH 3.0-5.0, Acetate;pH 5.0-8.0, K-phosphate; pH 8.0-9.0, Tris-HCI
Fig.5. Thermal stability
15 min-treatment with 20 mM K-phosphate buffer,pH 7.0 enzyme concn.: 2.0 U/mL
1. 原理
NADHの減少量を340nmにおける吸光度の変化で測定する。
2.定義
下記条件で1分間に1マイクロモルのNADHを酸化する酵素量を1単位(U)とする。
3.試薬
酵素溶液:酵素標品を予め氷冷した20 mM K-リン酸緩衝液,pH 7.0で溶解し,同緩衝液で0.2〜0.7 U/mLに希釈する。
4.手順
1.下記反応混液をキュベット(d=1.0 cm)に調製し,30 ℃で約5分間予備加温する。
1.77 | Tris-HCl緩衝液 | (A) |
0.30 | Na2CO3 水溶液 | (B) |
0.30 | K-Phosphoenolpyruvate水溶液 | (C) |
0.03 | MgSO4 水溶液 | (D) |
0.30 | NADH水溶液 | (E) |
0.30 | Malate dehydrogenase溶液 | (F) |
2.酵素溶液0.1 mLを添加し,ゆるやかに混和後,水を対照に30 ℃に制御された分光光度計で340 nmの吸光度変化を3〜4分間記録し,その初期直線部分から1分間当りの吸光度変化を求める(ΔODtest)。
3.盲検は,酵素溶液の代わりに酵素希釈液を0.1 mL加え,上記同様に操作を行って1分間当たりの吸光度変化を求める(ΔODblank)。
5.計算式
U/mL =
ΔOD/min (ΔOD test−ΔOD blank)×3.1(mL)×希釈倍率
6.22×1.0×0.1(mL)
= ΔOD/min×4.984×希釈倍率 | |
U/mg | = U/mL×1/C |
6.22 | : NADHのミリモル分子吸光係数(cm2/micromole) |
1.0 | : 光路長(cm) |
C | : 溶解時の酵素濃度(c mg/mL) |
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