EVIDENCE FOR 1-(MALONYLAMINO) CYCLOPROPANE-1-CARBOXYLIC ACID BEING THE MAJOR CONJUGATE OF AMINOCYCLOPROPANE-1-CARBOXYLIC ACID IN TOMATO FRUIT

Tomato (Lycopersicon esculentum Miller) fruit discs fed with [2,3-C-14 ]1-aminocyclopropane-1-carboxylic acid (ACC) formed 1-malonyl-ACC (MAC C] as the major conjugate of ACC in fruit throughout all ripening stag es, from immature-green through the red-ripe stage. Another conjugate of ACC, gamma-glutamyl-ACC (GACC), was formed only in mature-green fru it in an amount about 10% of that of MACC; conjugation of ACC into GAC C was not detected in fruits at other ripening stages. No GACC formati on was observed from etiolated mung bean (Vigna radiata [L.] Wilczek) hypocotyls, etiolated common vetch (Vicia sativum L.) epicotyls, or pe a (Pisum sativum L.) root tips, etiolated epicotyls, and green stem ti ssue, where active conversion of ACC into MACC was observed. GACC was, however, formed in vitro in extracts from fruit of all ripening stage s. GACC formation in an extract from red fruit at pH 7.15 was only abo ut 3% of that at pH 8.0, the pH at which most assays were run. Our pre sent in vivo data support the previous contention that MACC is the maj or conjugate of ACC in plant tissues, whereas GACC is a minor, ii any, conjugate of ACC. Thus, our data do not support the proposal that GAC C formation could be more important than MACC formation in tomato frui t.