Abstract
New methods for the determinations of monoamine oxidase (MAO) activities were presented using benzylamine (BZA-oxidase) or n-butylamine (NBA-oxidase) as substrates, in which the amounts of ammonia liberated by the enzyme actions were measured by means of the direct colorimetric method of Okuda and Fujii. BZA-oxidase was higher than NBA-oxidase in liver extract, but the relation was reversed in serum. It was felt that MAO found in liver and in serum might not be the same. Serum MAO activities increased more markedly in liver cirrhosis and hepatic cancer than in acute or chronic hepatitis. It was interesting enough that the increased serum MAO activities were closely related with the grades of fibrosis determined histologically. It was considered that the n-butylamine was the preferable substrates than the benzylamine for the determination of serum MAO activities, because NBA-oxidase activities were higher than those of BZA-oxidase in human serum.
