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Alcohol dehydrogenase isoenzymes were isolated from the liver of patients with hepatoma and healthy control individuals. Whereas only a single form of the enzyme was obtained in healthy control liver, two distinct forms of the enzyme were found in hepatoma liver. These two forms were named AD-I and AD-II according to their elution pattern in CM-cellulose chromatography and mobility towards the anode in polyacrylamide gel electrophoresis. Both isoenzymes resembled normal liver enzyme with respect to their molecular properties. However, the two forms had distinct kinetic properties, although AD-I had some properties similar to the normal liver enzyme. The Km values of AD-I for ethanol, n-butanol and m-nitrobenzyl alcohol were 61 microM, 90 microM and 292 microM, respectively, as against the values for AD-II which were 473 microM, 100 microM and 60 microM for the respective substrates. Pyrazole inhibited the activity of AD-II but not that of AD-I. These kinetic properties of alcohol dehydrogenase in patients with hepatoma could be of clinical importance particularly in the tropics where the disease is prevalent.

The serum activity of alcohol dehydrogenase was determined in healthy controls and in patients with liver diseases. The mean activity in hepatoma (6.4 +/- 1.0U/L) was significantly higher (P less than 0.05) than the mean values in liver cirrhosis (2.7 +/- 0.5U/L); hepatitis (4.3 +/- 1.0U/L), obstructive jaundice (2.9 +/- 0.5U/L) and healthy controls (0.7 +/- 0.1U/L). Alcohol dehydrogenase purified by CM-cellulose chromatography from the sera of patients with hepatoma had a higher affinity for butanol long chain saturated and unsaturated alcohols than the purified enzyme from healthy controls. Similarly, hepatoma alcohol dehydrogenase oxidized ethanol very poorly (KM = 154 microM) when compared with that from healthy controls (KM = 40.2 microM). Hepatoma alcohol dehydrogenase was inhibited by pyrazole while those of other liver diseases and the healthy controls were not. These properties of serum alcohol dehydrogenase may prove useful in the early diagnosis of hepatoma since biochemical changes occur before morphological changes in the development of cancer.