Glucose is linked to haemoglobin through
*When blood glucose enters the erythrocytes, it glycates the e-amino group of lysyl residues and the amino terminals of hemoglobin.*The fraction of hemoglobin glycated, normally about 5%, is propoionate to blood glucose concentration.*Since the half-life of an erythrocyte is typically 60 days, the level of glycated hemoglobin (HbA1c) reflects the mean blood glucose concentration over the preceding 6 to 8 weeks.*Measurement of HbA 1c therefore provides valuable information for management of diabetes mellitus.*Enzymatic addition of any sugar to a protein is called " glycosylation", while non-enzvmatic process is termed "glycation".*Interpretation of HbA1C valuesHbA1C valuesInterpretation <5.5 % Normal 5.5 - 7 % Adequate control 7 - 8 % Inadequate control 8 - 9 % Poor control Any values between 5.6 and 6 .4 are to be considered as impaired glucose tolerance. Value above 6 .5 % is considered as diabetic Harper's illustrated Biochemistry ,30th ed ,page 59
N-linkage
O-linkage
C-C linkage
O-H linkage
Metabolism of carbohydrate