1. Serum
carnosinase activity was assayed in a group of alcoholic patients with and without histologically proven
atrophy of type II skeletal muscle fibres, and in control subjects. No significant activity was detected in muscle biopsy samples or washed erythrocytes. 2. Serum
carnosinase activity was significantly lower in chronic alcoholic patients compared with a group of age-matched controls. Alcoholics with abnormal muscle biopsies had significantly lower
enzyme activities than either those patients with normal muscle biopsies or the controls. Serum
enzyme activities in patients with normal muscle biopsies were not significantly different from controls. 3. Serum
carnosinase activity was inversely correlated with the degree of
muscle atrophy as measured by the type II fibre
atrophy factor. There was a positive correlation between the
enzyme activity and skeletal muscle mass as reflected by the
creatinine-height index. Furthermore, the
enzyme activity significantly increased, with resolution or improvement in the
myopathy, in patients who abstained from alcohol. 4. Kinetic studies showed that the reduced
carnosinase activity was due mainly to a decrease in the apparent Vmax. The apparent Km was significantly higher in the myopathic compared with non-myopathic alcoholics. Mixing serum from controls and patients with
myopathy gave the expected values, indicating the absence of a serum
enzyme inhibitory factor. Acute alcohol loading had no effect on the serum
carnosinase activity. 5. The decrease in serum
carnosinase activity in alcoholics was not related to the severity of their
liver disease. Assays of serum
carnosinase in chronic alcoholics, can thus be used as a marker of their associated
myopathy.