You decide to perform assays to check the activity of one or more metabolic enzymes in the red blood cells. Which enzyme (s) would you check, and why? (keep answer as simple as possible please)

 

The enzyme (s) I  would check include-

• In Liver RBCs arginase (EC 3.5.3.1) or argininosuccinate , to rule out liver pathology .
• Also deficiencies of most of the enzymes of the oxidative hexose monophosphate shunt and the anaerobic Embden-Meyerhof pathways like Glucose 6 Phosphate Dehydrogenase (G-6-PD) deficiency and Pyruvate Kinase (PK) deficiency are the most common.

Step-by-step explanation

Normally red blood cells are less useful from this point of view because they while maturation looses many of the enzymes  present in nucleated cells; nevertheless some enzymes which normally would be assayed in Liver, eg, arginase (EC 3.5.3.1) or argininosuccinate lyase (EC 4.3.2.1), can be measured in red cells if a liver biopsy is not available.

• Apart from this, enzyme activities are assayed in red cells because of a primary  enzyme defect of these cells, as for example in certain haemolytic anaemias . Deficiencies of most of the enzymes of the oxidative hexose monophosphate shunt and the anaerobic Embden-Meyerhof pathways have been seen but Glucose 6 Phosphate Dehydrogenase (G-6-PD) deficiency and Pyruvate Kinase (PK) deficiency are the most common.
• G-6-PD is an X-linked inherited disorder, and is the most common, affecting persons of Mediterranean, African, Asian, or Middle Eastern decent.
• Hereditary non-spherocytic hemolytic anemia  also occur as a consequence of other enzyme deficiencies. The most common and best defined deficiency of the Embden-Myerhof pathway is pyruvate kinase (PK) deficiency. Clinically affected individuals are homozygote or double heterozygotes for abnormal PK genes.