PURIFICATION AND SYNTHESIS UNDER ANAEROBIC CONDITIONS OF RICE ARGININE DECARBOXYLASE

Arginine decarboxylase (ADC; EC 4.1.1.19) which catalyzes the synthesis of putrescine, is involved in the responses of plants to stress. The enzyme was purified 1,561-fold from rice coleoptiles by steps that included ammonium sulfate fractionation, gel filtration, ion-exchange chromatography and chromatofocusing. The purified enzyme had a pI of 5.3, a molecular mass of 176 kDa and appeared to be composed of three subunits of 63 kDa. A polyclonal antibody was raised in a rabbit and the IgG fraction was purified from serum. On Western blots the antibody recognized the ADC from both rice and E. coli. Immunoprecipitation with the ADC-specific antibodies allowed detection of radiolabelled ADC in extracts from aerobically and anaerobically grown rice seedlings that had been supplied with a mixture of C-14-amino acids. This result is discussed in relation to the role of ADC under anaerobic conditions.