Immunoaffinity purification and characterization of glyceraldehyde-3-phosphate dehydrogenase from human erythrocytes

摘要

A new procedure utilizing immunoaffinity column chromatography has been used for the purification of glyceraldehyde-3-phosphate dehydrogenase(GAPDH,EC 1.2.1.12)from human erythrocytes.The comparison between this rapid method(one step)and the traditional procedure including ammonium sulfate fractionation followed by Blue Sepharose CL-6B chromatography shows that the new method gives a highest specific activity with a highest yield in a short time.The characterization of the purified GAPDH reveals that the native enzyme is a homotetramer of ～150 kDa with an absolute specificity for the oxidized form of nicotinamide adenine dinucleotide(NAD+).Western blot analysis using purified monospecific poly clonal antibodies raised against the purified GAPDH showed a singie 36 kDa band corresponding to the enzyme subunit.Studies on the effect of temperature and pH on enzyme activity revealed optimal values of about 43℃ and 8.5, respectively.The kinetic par ameters were also calculated:the Vmax was 4.3 U/mg and the Km values against G3P and NAD+ were 20.7and 17.8μM,respectively.The new protocol described represents a simple,economic,and reproducible tool for the purification Of GAPDH and can be used for other proteins.