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Test ID: GALTP    
Galactose-1-Phosphate Uridyltransferase Biochemical Phenotyping, Erythrocytes

Method Description Describes how the test is performed and provides a method-specific reference

Isoelectric focusing is used to resolve the isoenzymes of galactose-1-phosphate uridyltransferase (GALT). The band patterns, when used in conjunction with a quantitative GALT result, can be used to predict the GALT phenotype of an individual.

 

In isoelectric focusing, a pH gradient is established across an agarose gel by adding a select mixture of amphoteric molecules to the gel and applying an electric field to the gel. Each protein (isoenzyme) has its own unique isoelectric point, a pH at which the net charge of the protein is equal to zero. Therefore, if a protein is applied to the gel, it will migrate through the pH gradient in the gel until it reaches its isoelectric point. There the protein will stop and "focus" into distinct bands.

 

In this procedure, an RBC hemolysate is focused on a 5% agarose gel containing ampholytes of a 5 to 7 pH range. The isoenzyme bands are then visualized by applying a substrate mixture that results in a series of reactions (shown below). The final product, nicotinamide adenine dinucleotide phosphate (NADPH; reduced form), is stained a blue-violet color when it reacts with phenazine methosulfate (PMS) and 3-(4-5 dimethylthiazol-2-yl)I-2,5-diphenyltetrazolium bromide (MTT).(Shin YS, Niedermeier HP, Endres W, et al: Agarose gel isoelectrofocusing of UDP-galactose pyrophosphorylase and galactose-1-phosphate uridyltransferase: developmental aspect of UDP-galactose pyrophosphorylase. Clin Chim Acta 1987;166:27-35, modified to acrylamide as described by Leclerc P, Forest JC: Electrophoretic determination of isoamylases in serum with commercially available reagents. Clin Chem 1982;28:37-40)

    

 

GALT

 

Gal-1-P + UDP-Glu

------------->

UDP-Gal + Glu-1-P

 

Phosphoglucomutase

 

Glu-1-P + Glu-1-6 diP

------------->

Glu-1-6 diP + Glu-6-P

 

Glu-6-P-Dehydrogenase

 

Glu-6-P + NADP

------------->

Ribose-5-P + CO(2) + NADPH

NADPH + MTT + PMS

------------->

Blue Violet Stain

 

PDF Report Indicates whether the report includes an additional document with charts, images or other enriched information

No

Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.

Thursday; 9 a.m.

Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.

8 days

Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result

15 days

Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

Processed RBC stored 2 months

Performing Laboratory Location The location of the laboratory that performs the test

Rochester