Molecular forms of arginine decarboxylase in oat leaves

RUIZ O.A., BORTOLOTTI C., TIBURCIO A.F. AND ALTABELLA T

PHYSIOLOGIA PLANTARUM

Año: 2000 vol. 108 p. 370 - 375

0031-9317

Arginine decarboxylase (ADC, EC 4.1.1.19) is the first enzyme in one of the two biosynthetic pathways of putrescine in plants and has been characterized from a number of species, beginning with the work of Smith (1979; Phytochemistry 18: 1447–1452) who suggested that oat ADC had native sizes of 118 and 195 kDa. There are several studies showing a lack of correlation between changes in enzyme activity and mRNA or protein levels. In oats (Avena sativa L.) a posttranslational modification of ADC has been described. The protein is synthesized as a 66-kDa precursor that is proteolytically processed into two polypeptides of 42 and 24 kDa with an associated gain of enzyme activity. In the present work, we have studied the existence of different ADC molecular forms in oat leaves by determination of enzymatic activity and using polyclonal antibodies obtained against an amino acid sequence near the C terminus deduced from the nucleotide sequence. In A7ena sati7a L. cv. Victory, we demonstrate the existence of 5 different molecular forms of ADC, with approximate molecular mass of 195, 115, 66, 38 and 23 kDa that react with our antibodies and have enzymatic activity. Our results agree with previous work, but this is the first report showing all molecular forms simultaneously and might be a preliminary contribution to solve the question about the distribution of multiple forms of ADC and their importance in the correlation between the enzymatic activity and mRNA levels.