產品貨號：K-LACGAR 

品牌：Megazyme

產品品名：D-乳糖檢測試劑盒

英文品名：Lactose/Galactose (Rapid) Assay Kit

規格型號：115 assays per kit 

For the rapid assay of lactose, D-galactose and L-arabinose in food andplant products. Galactose dehydrogenase can be used to measure bothD-galactose and L-arabinose. Suitable for the analysis of lactose in“low-lactose” or “lactose-free” samples which contain high levels of monosaccharides. 

INTRODUCTION:

Lactose, or milk sugar, is a white crystalline disaccharide. It is formed
in the mammary glands of all lactating animals and is present in their
milk. Lactose yields D-galactose and D-glucose on hydrolysis by
lactase (β-galactosidase), an enzyme found in gastric juice. People
who lack this enzyme after childhood cannot digest milk and are said
to be lactose intolerant. Common symptoms of lactose intolerance
include nausea, cramps, gas and diarrhoea, which begin about 30
minutes to 2 hours after eating or drinking foods containing lactose.
Between 30 and 50 million Americans are lactose intolerant, with
certain ethnic and racial populations being more widely affected than
others; as many as 75 percent of all African-Americans and Native
Americans and 90 percent of Asian-Americans are lactose intolerant.
The condition is least common among persons of northern European
descent.
Enzymic methods for the measurement of lactose are well known and
are generally based on the hydrolysis of lactose to D-galactose and
D-glucose with β-galactosidase, followed by determination of either
D-galactose or D-glucose. In the International Dairy Federation
Method (79B:1991) for the measurement of lactose in “dried
milk, dried ice-mixes & processed cheese”, details are given for
deproteinisation of samples, hydrolysis of lactose with β-galactosidase
and measurement of either released D-galactose or D-glucose.
The measurement of lactose as D-galactose liberated is more
generally reliable than measurement as D-glucose liberated because
preparations generally contain more free D-glucose than free
D-galactose.
Enzymic kits for the determination of D-galactose are very slow. This
is due to the low rate of natural chemical “mutarotation” between
the α- and β-anomeric forms of D-galactose. Only the β-form is
recognised by β-galactose dehydrogenase. In incubations containing
NAD+, D-galactose and β-galactose dehydrogenase, there is a very
rapid initial increase in absorbance due to the consumption of β-Dgalactose,
and this is followed by a very slow approach to the endpoint.
This very slow approach results from the very low rate of
chemical “mutarotation” of α-D-galactose into β-D-galactose. Using
technology developed by Megazyme (patent pending), a galactose
mutarotase has now been incorporated into the assay format to
rapidly catalyse this rate-limiting mutarotation step. The result is very
rapid analysis times of approx. 5 min at room temperature (Figure 1).

KITS:

Kits suitable for performing 115 assays are available from Megazyme.
The kits contain the full assay method plus:
Bottle 1: Buffer (2.5 mL, pH 5.0).
Stable for > 2 years at 4°C.
Bottle 2: Buffer (25 mL, pH 8.6) plus EDTA and sodium azide
(0.02% w/v) as a preservative.
Stable for > 2 years at 4°C.
Bottle 3: NAD+.
Stable for > 5 years at -20°C.
Bottle 4: β-Galactosidase suspension (1.2 mL).
Stable for > 4 years at 4°C.
Bottle 5: β-Galactose dehydrogenase plus galactose mutarotase
suspension, 2.4 mL.
Stable for > 2 years at 4°C.
Bottle 6: D-Galactose standard solution (5 mL, 0.4 mg/mL in
0.02% w/v sodium azide).
Stable for > 2 years at 4°C.

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