The analysis of soluble galactosyltransferase isoenzyme patterns using high resolution agarose isoelectricfocusing

A high resolution method has been developed to separate the isoenzymes of galactosyltransferase by combining isoelectricfocusing (IEF) in 245 mm long agarose gels with a highly sensitive enzyme activity assay. The resolution and sensitivity is such that the isoenzyme pattern of 10 microliters human serum can be resolved. Using this method normal human serum was shown to contain at least 12 isoenzyme forms of galactosyltransferase, the major forms having isoelectric points of 4.33, 4.43, 4.51, 4.61, 4.74, 4.87, 4.96, 5.16 and 5.23. Part of the isoenzyme pattern complexity is due to sialylation of some isoenzymes. Alpha-lactalbumin-affinity chromatography, a method widely used in the purification of galactosyltransferase, causes a preferential purification of some of the isoenzyme forms.