Lysozyme Assay

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Lysozyme Assay

Method

The rate of lysis of Micrococcus lysodeikticus is determined as suggested by Shugar (1952). One unit is equal to a decrease in turbidity of 0.001 per minute at 450 nm at pH 7.0 and 25°C under the specified conditions. A wide range of activities are reported for pure lysozyme preparations under these conditions. The Worthington specific activity of 8,000 u/mg dw is equivalent to 50,000 u/mg dw claimed by other suppliers.

Reagents

0.1 M Potassium phosphate, pH 7.0
Micrococcus lysodeikticus cells: Prepare by suspending 9 mg of dried Micrococcus lysodeikticus (Worthington code: ML) cells in 25 ml of 0.1 M potassium phosphate buffer, pH 7.0. Dilute to a final volume of 30 ml with the same buffer.

Enzyme

Dissolve the enzyme at a concentration of one mg/ml in cold reagent grade water. Keep cool until assay. Immediately prior to assay, dilute to a concentration of 150-500 units/ml with reagent grade water. (The rate should fall between 0.015-0.040 ΔA₄₅₀/minute).

Procedure

Adjust spectrophotometer to 450 nm and 25°C.

Pipette 2.9 ml of Micrococcus lysodeikticus cell suspension into a cuvette and incubate for 4-5 minutes in order to achieve temperature equilibration and to establish blank rate, if any. Add 0.1 ml of appropriately diluted enzyme to cuvette and record the change in A₄₅₀ per minute from the initial linear portion of the curve.

Calculation

\frac{\text{Units}}{\text{mg}}\text{ = } \frac{\frac{\Delta \text{A}_{450}}{\text{min}}\text{ x 1000}}{\text{mg enzyme in reaction mixture}}

\frac{\text{MgP}}{\text{ml}}\text{ = } \text{A}_{280}\text{ x 0.39}

Lysozyme Products

Description

Lysozyme

Source:

Egg White

A powder containing trace amounts of sodium chloride.

Store at 2-8°C.

…

Activity

≥5,000 units per mg dry weight

Certificate of Analysis

Code

Product details

LS002880

1 gm

$29.00

LS002881

10 gm

$152.00

LS002883

Bulk

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Description

Lysozyme, Purified, Salt Free

Source:

Egg White

Two times crystallized. A dialyzed, lyophilized powder.

Store at 2-8°C.

…

Activity

≥8,000 units per mg dry weight

Certificate of Analysis

Code

LYSF

Product details

LS002931

1 gm

$36.00

LS002933

5 gm

$88.00

LS002934

Bulk

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Lysozyme - Assay

Lysozyme Assay

Lysozyme Products