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Lactate Dehydrogenase (LDH)

(L-Lactate: NAD+ oxidoreductase EC 1.1.1.27)

Lactate dehydrogenase (LDH) catalyzes the following reaction:

                  LDH
Pyruvate + NADH ------> Lactate + NAD+ + H+ 

LDH is a metabolic enzyme which is widely distributed in nature. Mammalian LDH exists as five tetrameric isozymes composed of combinations of two different subunits. The isozymes differ in physical, immunological and catalytic properties. LDH has a molecular weight of about 140,000.

LDH is of clinical significance in that the serum level of certain isozymes suggests pathological changes in particular tissues. It is also used extensively for the determination of lactate and in coupled systems for detection of biological metabolites.



1.Source: Porcine Heart
   Form: Freeze-dried powder 
   Solubility: Soluble in distilled water or dilute buffer 
   Stability: Store at -20 C (-4 F) 
   Activity: 350 U/mg protein 
   Protein: 80-90% (biuret) 
   Catalog No.: 092A0350 
$2.00/KU
2.Source: Porcine Muscle
   Form: Freeze-dried powder 
   Solubility: Soluble in distilled water or dilute buffer 
   Stability: Store at -20 C (-4 F) 
   Activity: 350 U/mg protein 
   Protein: 10 mg/ml (biuret) 
   Catalog No.: 093A0350 
$2.00/KU
3.Source: Porcine Muscle
   Form: Glycerol Solution 
   Solubility: Soluble in distilled water or dilute buffer 
   Stability: Store at 4 C (39 F); Do not freeze 
   Activity: 550 U/mg protein 
   Protein: 10 mg/ml (biuret) 
   Catalog No.: 093C0550 
$2.00/KU
4.Source: Rabbit Muscle
   Form: Freeze-dried powder 
   Solubility: Soluble in distilled water or dilute buffer 
   Stability: Store at -20 C (-4 F) 
   Activity: Approximately 350 U/mg protein 
   Protein: Approximately 90% (biuret) 
   Catalog No.: 094A0350 
$2.00/KU
5.Source: Chicken Heart
   Form: Freeze-dried powder 
   Solubility: Soluble in distilled water or dilute buffer 
   Stability: Store at -20 C (-4 F) 
   Activity: 300 U/mg solid 
   Protein: 10 mg/ml 
   Catalog No.: 127A0300 
$5.00/KU
6.Source: Porcine Heart
   Form: Ammonium sulfate suspension 
   Solubility: Soluble in distilled water or dilute buffer 
   Stability: Store at 4 C (39 F); Do not freeze 
   Activity: 350 U/mg protein 
   Protein: 20 mg/ml 
   Catalog No.: 092B0350 
$2.00/KU
7.Source: Porcine Muscle
   Form: Ammonium sulfate suspension 
   Solubility: Soluble in distilled water or dilute buffer 
   Stability: Store at 4 C (39 F); Do not freeze 
   Activity: 550 U/mg protein 
   Protein: 20 mg/ml 
   Catalog No.: 093B0550 
$2.00/KU
8.Source: Bovine Heart
   Form: Freeze-dried powder 
   Solubility: Soluble in distilled water or dilute buffer 
   Stability: Store at -20 C (-4 F) 
   Activity: 300 U/mg protein 
   Protein: 10 mg/ml 
   Catalog No.: 195A0300 
$2.00/KU
9.Source: Human Heart
   Form: Ammonium sulfate suspension 
   Solubility: Soluble in distilled water or dilute buffer 
   Stability: Store at 4 C (39 F); Do not freeze 
   Activity: 50-100 U/mg protein 
   Protein: 10 mg/ml (biuret) 
   Catalog No.: 060B0050 
$2.00/U
10.Source: Human Heart
   Form: Ammonium sulfate suspension 
   Solubility: Soluble in distilled water or dilute buffer 
   Stability: Store at 4 C (39 F); Do not freeze 
   Activity: 350 U/mg protein 
   Protein: 10 mg/ml (biuret) 
   Catalog No.: 170B0350 
$2.00/U
11.Source: Human Muscle
   Form: 50% Glycerol solution 
   Solubility: Soluble in distilled water or dilute buffer 
   Stability: Store at 4 C (39 F); Do not freeze 
   Activity: 200 U/mg 
   Protein: 10 mg/ml 
   Catalog No.: 193C0200 
$2.00/U


The amount of enzyme which will reduce one micromole of pyruvate to L-lactate per minute at 25C in 0.1 M phosphate buffer at pH 7.0.


The rate of decrease in the absorbancy at 340 nm, resulting from the oxidation of NADH, is a measure of LDH activity.


  1. 0.1 M Sodium phosphate buffer, pH 7.0.
  2. Sodium pyruvate solution, (2.5 mg/ml) in distilled water.
  3. NADH solution (5 mg/ml). Dissolve 5 mg NADH, sodium salt in 1.0 ml distilled water. Always prepare fresh.
  4. 1% Bovine serum albumin (BSA) solution. Dissolve 1.0 g BSA in 100 ml distilled water. Albumin should be of highest purity.
  5. LDH solution (0.5-1.0 U/ml) - Dilute 0.1 ml enzyme suspension to 5 ml with cold 1% BSA solution. Use an aliquot from this stock enzyme solution and dilute to a final concentration of 0.5-1.0 U/ml with cold 1% BSA. This solution must be used as soon as it is prepared and must be made fresh for each run.



  1. Set spectrophotometer (equipped with strip chart recorder and temperature control) at 340 nm and 25C.
  2. Into the cuvette, pipette the following:
    0.1 M Phosphate buffer, pH 7.0 2.7 ml
    Sodium pyruvate 0.1 ml
    NADH 0.05 ml
  3. Mix and incubate at 25C for 5 minutes.
  4. Transfer the cuvette to the spectrophotometer and record the blank rate for 2-3 minutes.
  5. Pipette 0.1 ml fresh enzyme solution (0.5-1.0 U/ml). Mix and monitor the reaction for 5-10 minutes at 340 nm.
  6. Calculate (delta)E340 nm/min



Activity (U/mg) = (ΔE304nm/min)(Total Vol.)(Enz. Diln.)
(6.22)(Enz. Vol.)(mg Enz./ml)
 

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