['Methacrylyl-coenzyme A (MC-CoA) hydratase and beta-hydroxyisobutyryl-coenzyme A (HIB-CoA) hydrolase are key enzymes regulating the toxic concentration of MC-CoA generated in valine catabolism.', 'We studied the activities and mRNA expression levels of these enzymes in normal human livers and in human livers with chronic hepatitis, cirrhosis, or hepatocellular carcinoma.', 'The activities of both enzymes were significantly lower by 36% to 46% in livers with cirrhosis or hepatocellular carcinoma compared with normals, suggesting a decrease in the capability of detoxifying MC-CoA with these diseases. The mRNA levels for both enzymes measured by quantitative polymerase chain reaction were significantly increased in livers with cirrhosis, but were not altered in those with chronic hepatitis or hepatocellular carcinoma when compared with normal livers.'] Does human liver disease decrease methacrylyl-CoA hydratase and beta-hydroxyisobutyryl-CoA hydrolase activities in valine catabolism?