The oxidation of amines by extracts of pea seedlings

Abstract

A colorimetric test, based on the oxidation of added Mn++ to Mn-++, is described for the detection of H2O2 in plant extracts. By means of this test evidence was obtained that H2O2 is produced by enzyme systems present in extracts of many higher plants. The oxidation of both mono- and diamines is catalysed by extracts of pea and lupine seedlings and leaves of lavender and red clover. It is not yet known whether this is due to the presence of specific mono- and diamine oxidases. With the growth conditions used, activity appears in pea seedlings, mainly in the cotyledons, 3-4 days after germination and is maximal over the period 7-18 days. Only slightly activity is found in the adult plant. Diamines, in particular putrescine and cadaverine, are more readily attacked than monoamines. Of the monoamines tested beta-phenylethylamine and di-beta-phenylethylamine are most readily attacked. The oxidative deamination of beta-phenylethylamine and putrescine is catalysed according to the equation R.CH2NH2 + O2 + H2O[long dash][forward arrow] R.CHO + H2O2 + NH3 As with animal diamine oxidase only one of the terminal amino groups is attacked. The phenylacetaldehyde formed by the action of the plant amine oxidase on beta-phenylethylamine was oxidized by an aldehyde oxidase present in the prepn. used. It is suggested that 3-indolylacetic acid may be formed by the successive action of the plant amine oxidase and of the aldehyde oxidase on tryptamine.