RESUMO
The report describes results of separation of sialyltransferase isoenzymes by electrofocusing plasma from healthy volunteers and patients having different types of malignant tumour. Extensive modification of the technique was adopted in determining enzyme activity, such as elution of gel strips with the buffer pH corresponding to the gel focusing point; assessment of the effect of different pH on endogenous incorporation of radioactivity to desialated fetuin; and quantitative analysis of protein present in each gel band for calculation of enzyme activity. Plasma from normal individuals showed the existence of 5 sialyltransferase isoenzymes at pI 4.8, 5.5, 6.3, 6.8 and 7.5. There were higher isoenzyme activities in plasma samples from patients afflicted with malignancy of lungs and colon in comparison to normal pattern. Endometrial and breast cancer patients also showed elevated levels of the enzyme which could be controlled by surgery and combined therapies with cytotoxic drugs and radiation, respectively. The observations suggest the potential use of sialyltransferase as a tool for tumour diagnosis, and are discussed in relation to prognosis of the disease in the course of therapy.