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Activities and Isoenzyme Patterns of Some Enzymes of Glucose Metabolism in Human Primary Malignant Hepatoma¹

Enzyme Research Unit, South African Institute for Medical Research, Johannesburg, South Africa

The levels of a number of enzymes of carbohydrate metabolism were assayed in the cancerous and morphologically normal (host) portions of livers from nine primary malignant hepatoma cases obtained at autopsy. The levels of these enzymes in two normal human adult and two fetal livers were also determined. The activities of phosphoglucomutase, fructose 1,6-diphosphatase and -glycerophosphate dehydrogenase were considerably lower in the tumor tissue than in host tissue or tissue from normal adult livers. Other enzymes that showed decreased activity in tumor relative to host tissue included triosephosphate isomerase, glyceraldehyde phosphate dehydrogenase, phosphoglycerate kinase, phosphoglycerate mutase, and lactate and malate dehydrogenases.

Pyruvate kinase activity was somewhat elevated in the tumor. More striking changes were seen on electrophoresis, which showed that the major L isoenzyme of liver was replaced by the more positively charged M band. Hexokinase activity showed no consistent changes in level in hepatoma, but starch gel electrophoresis showed the appearance of hexokinase II and disappearance of hexokinase III in tumor tissue. Glucokinase was not detected in any preparations.

An increase in the proportion of lactate dehydrogenase Isoenzyme 3 was found for one cancer patient. No differences in the electrophoretic patterns of -glycerophosphate dehydrogenase or triosephosphate isomerase were seen between cancer, host, or normal liver tissue. The ratio of activity of tumor aldolase with fructose 1,6-diphosphate to that with fructose 1-phosphate was considerably increased, showing a change from the liver type B to admixture with muscle type A.

¹ This work was supported in part by a grant awarded to Dr. Balinsky from the Medical Research Council of South Africa.

² To whom reprint requests and correspondence should be addressed

³ This study forms part of a thesis submitted for a Ph.D. degree.

⁴ Present address: Crown Mines Bantu Hospital, Crown Mines, Transvaal, South Africa.

Received 1/25/72. Accepted 10/20/72.