Demonstration and some properties of N-acetyl-beta,D-hexosaminidase (HEX) C isoenzyme in human renal tissues: relative increase of HEX C activity in renal cell carcinoma.

The present study has demonstrated the presence of hexosaminidase (HEX) C activity in human renal tissues by an electrophoretic method. At the same time, its enzymatic properties, obtained as unbound fraction of renal tissue extracts passed through a concanavalin A Sepharose column, have been compared with those of HEX A and B. HEX C had the fastest electrophoretic mobility among HEX isoenzymes. The optimal pH of HEX C was 6.5, while that of HEX A and B was 4.9. The Km value of HEX C for synthetic glucosaminide substrate was 1.16 mmol/l, while that of HEX A and B was 0.18 mmol/l and 0.22 mmol/l, respectively. HEX C was inactive for a synthetic galactosaminide substrate, while HEX A and B were active. The percentage of HEX C activity to the total was 7.9 +/- 2.9% and 13.8 +/- 3.0% in the normal and the neoplastic tissues, respectively. A significant difference was observed between them (P < 0.01). These results indicate that the enzymatic properties of HEX C is quite different from those of A and B and also suggest that the determination of HEX C may become one of the useful clinical markers of the human renal cell carcinoma.