Oxidation of glucosamine by human polymorphonuclear leukocytes

Area of Science:

• Cellular metabolism
• Immunology
• Biochemistry

Background:

• Human polymorphonuclear leukocytes (PMNs) are key immune cells involved in phagocytosis.
• Understanding the metabolic pathways utilized by PMNs during activation is crucial for immune response research.

Purpose of the Study:

• To investigate the metabolic fate of glucosamine in human PMNs upon stimulation.
• To compare the oxidative pathways of glucosamine and glucose in PMNs.

Main Methods:

• Incubation of human PMNs with opsonized zymosan to induce phagocytosis.
• Measurement of 14CO2 production from [1-14C]glucosamine and [1-14C]glucose.
• Assessment of the role of the hexosemonophosphate shunt (HMPS) and specific enzymes like glucose-6-phosphate dehydrogenase.

Main Results:

• PMNs produced CO2 from glucosamine at 10-25% the rate of glucose, indicating glucosamine utilization.
• Glucosamine oxidation was dependent on HMPS activation and inhibited by glucose, suggesting pathway overlap.
• Key HMPS enzyme glucose-6-phosphate dehydrogenase did not act on glucosamine-6-phosphate, and sonically disrupted PMNs failed to oxidize glucosamine, indicating a requirement for intact cells.

Conclusions:

• PMNs likely convert glucosamine into a substrate compatible with HMPS enzymes for oxidation.
• This conversion process requires intact PMNs and potentially an unidentified cofactor.
• The metabolic pathway for glucosamine oxidation in PMNs differs from that of glucose.