Pyruvate Kinase, Red Blood Cell

Updated: 2026-08-25

Overview

Pyruvate kinase, red blood cell (PK-R) is the erythrocyte-specific isoform of the glycolytic enzyme pyruvate kinase (EC 2.7.1.40), encoded by the PKLR gene. As the terminal enzyme of glycolysis, it catalyzes the irreversible conversion of phosphoenolpyruvate to pyruvate with concomitant ATP generation. Deficiencies in PK-R cause hereditary non-spherocytic hemolytic anemia (PK deficiency), the most common enzymatic defect of glycolysis in erythrocytes. The enzyme's tetrameric structure (comprising R-type subunits) exhibits unique allosteric regulation by fructose-1,6-bisphosphate (FBP), distinguishing it from other tissue isoforms.

Physical and Chemical Properties

PK-R is a ~62 kDa homotetrameric protein with optimal activity at pH 7.0-7.5. It requires Mg2+ and K+ ions as cofactors and demonstrates hyperbolic kinetics with its substrate phosphoenolpyruvate (PEP). The enzyme's stability is temperature-sensitive, with rapid degradation above 37°C. Lyophilized formulations typically retain activity for 2-3 years when stored at -20°C, while liquid preparations require -80°C storage with cryoprotectants to prevent aggregation. Activity assays commonly measure NADH oxidation coupled to lactate dehydrogenase (LDH) at 340 nm.

Main Applications

In clinical diagnostics, PK-R activity assays are essential for confirming PK deficiency anemia, with testing indicated for chronic hemolysis with negative direct antiglobulin tests. Commercial test kits typically measure enzyme activity in hemolysates at 37°C. Research applications include studies of erythrocyte metabolism, enzyme kinetics, and allosteric regulation. Recombinant PK-R is used in structural biology (X-ray crystallography) and drug discovery targeting hemolytic disorders. Some bioprocessing workflows utilize PK-R as an ATP-regeneration system.

Safety and Storage

PK-R poses minimal safety risks (non-toxic, non-flammable) but should be handled with standard laboratory precautions including gloves and eye protection. Avoid repeated freeze-thaw cycles of liquid preparations. For long-term storage, lyophilized powder should be kept at -20°C in sealed containers with desiccant. Reconstituted solutions should be aliquoted and stored at -80°C with 20-50% glycerol. Activity loss occurs rapidly at room temperature (>50% in 24 hours).

B2B Procurement Guide

When sourcing PK-R, verify: 1) Activity specifications (typically 100-400 units/mg protein), 2) Purity by SDS-PAGE (>90% preferred), and 3) Absence of stabilizers that may interfere with assays. Research-grade material costs $200-$800/mg, while diagnostic-grade (IVD-certified) commands premium pricing. Key suppliers include Sigma-Aldrich (P9136), Roche Diagnostics, and specialized enzyme manufacturers. Lead times for custom preparations may extend to 8-12 weeks. Request certificates of analysis documenting kinetic parameters and endotoxin levels for sensitive applications.