title: Enzymatic method for determination of CO2 in serum.
abstract: We describe an enzymatic method, requiring only 10 mul of serum, for determining CO2 as bicarbonate or dissolved gas. Phosphoenolpyruvate carboxylase catalyzes the reaction of HCO3- with phosphoenolypyruvate to give oxalacetate. The resulting NADH, in the presence of malate dehydrogenase, is oxidized to NAD+, and the decrease in absorbance at 340 nm is directly proportional to the amount of CO2 present in the sample. Reaction is complete in 3 to 6 min under assay conditions, and is linearly related to CO2 concentrations between 8 and 65 mmol/liter. Analytical recovery is 95-110% (average, 101%). Two laboratories compared values obtained by continuous-flow analysis. The resulting correlation coefficients were 0.966 and 0.987, values for the t-test were t(paired) equals 0.473 and t(paired) equals 0.334, and average day-to-day precisions (three concentrations) were 3.9% and 4.2%.
mesh_terms: D001322:Autoanalysis; D002245:Carbon Dioxide / Q000097:blood*; D002262:Carboxy-Lyases; D005069:Evaluation Studies as Topic; D006801:Humans; D008291:Malate Dehydrogenase; D010728:Phosphoenolpyruvate / Q000378:metabolism; D011786:Quality Control; D013056:Spectrophotometry, Ultraviolet
chemical_list: D002245:Carbon Dioxide; D010728:Phosphoenolpyruvate; D008291:Malate Dehydrogenase; D002262:Carboxy-Lyases