The Abacam glycogen assay measures glucose please note "Abcam's Glycogen Assay Kit is an easy and accurate assay to measure glycogen levels in biological samples. In the assay, glucoamylase hydrolyzes the glycogen to glucose which is then specifically oxidized to produce a product that reacts with OxiRed probe to generate color (570 nm) and fluorescence (Ex 535/Em 587). The assay can detect glycogen 0.0004 to 2 mg/ml." The typical assay employes glucose oxidase and peroxidase to emit various signals including electrical, colorimetric, fluorescent dependent on the instrument in which the kit is produced to be compatible. When employing a glycogen standard or a glucose standard typically results are expressed as weight / volume (ug/ml). When expressed as mmol/kg it is most accurate to state glycogen concentrations measured as xx mmol glucose/ kg tissue. Should kit cost be an issue I have attached a protocol which is very cost saving method.Also please note that any Mr glycogen contains the same quantity of glucose mg/mg.

Hi Frank,

Thank you for your answer. I understand that the kit measures glucose but the standard curve is presented as ug glycogen, therefore, the values obtained from the linear regression fit should also be presented as ug glycogen, should they not? Would you suggest using the mol weight of glucose to calculate xx glucose/kg tissue?

Finally, thank you for attaching the alternative method. We already have our samples which have been freeze dried and homogenised in water. What step would you suggest proceeding from in the attached protocol?

Kind regards,

José

Hi Jose,

I see your dilemma. You may want to run your assay with an additional standard curve (glucose at same weight/weight as the kit standards) to validate the assay for glycogen measured as glucose in mmol/kg using the Mr of glucose for conversion. Alternately, ask the supplier what the Mr (MW) of their glycogen standard is and explain you wish to report in mmol/kilogram tissue and what is the molecular weight of their glycogen standard. You then define the kit standard in your methods.

I ran a few literature searches which may help. Glycogen Molecular weight is frequently expressed in terms of its simplest subunit which is the branch chain of 4 glucose molecules i.e Mr = 666.5777 grams / mol. However you choose to express your measurements needs to be defined in your methods so any researcher can convert as needed for comparison to their data.

Hi Frank, thank you very much for all of your help with this matter. I have looked further into the literature and have found that, although not mentioned in the results section, previous investigators often express glycogen as mmol of glucose/kg tissue. Upon using the MW of glucose, the values we are obtaining match the literature more closely. Your answer definitely pointed me in the right direction so thank you once again!

José