Genetics of monoamine oxidase

Substrate-typic changes of platelet monoamine oxidase activity in sub-types of schizophrenia

Monoamine oxidase (MAO) activity has been measured in the platelets of controls (n = 42) and schizophrenic patients (n = 49) of three subtypes, using beta-phenylethylamine, p-tyramine, and tryptamine as substrates. Characteristic differences of MAO activity were observed between platelets of patients and controls; the differences were substrate-typic: decreased enzyme activity was found with all three substrates in platelets of the parnaoid subtype. With tryptamine, MAO activity was decreased in the platelets of all three sub-types of schizophrenia. With p-tyramine, MAO was low in patients with affective psychoses and paranoid schizophrenia. The value of MAO activity measurements as a means for distinguishing sub-types of schizophrenic disorders is improved by using two substrates; tryptamine and p-tyramine. Possible mechanisms of the substrate-typic changes of platelet MAO activity in schizophrenia are discussed.

Physiological and pathological changes in tissue monoamine oxidase activity

This article explores the possibility that malfunction of the enzyme monoamine oxidase (E.C. 1.4.3.4., MAO) could lead to aberrations in the catabolism of biogenic amines in the central nervous system and give rise to certain mental abnormalities. No conclusive evidence could be presented to substantiate this. Data on the normal function of the enyzme (for example its existence in multiple forms, the control of MAO activity by hormones or the independent development of MAO activities towards different substrates during maturation) are reviewed.