Activities of Sulfhydryl-Related and Phenylpropanoid-Synthesizing Enzymes during Leaf Development of Arabidopsis thalillna

Activities of Sulfhydryl-Related and Phenylpropanoid-Synthesizing Enzymes during Leaf Development of Arabidopsis thalillna

Activities of glutathione- and thioredoxin-related enzymes and phenylpropanoid-synthesizing enzymes were measured and compared in the developing leaves of Arabidopsis thaliana. Phenylalanine ammonia-lyase activity is maximal in the leaves of 2-wk-grown Arabidopsis. Tyrosine ammonia-lyase activity is maximal in the leaves of 3-wk-grown and 4-wk-grown Arabidopsis. Activity or thioltransferase, an enzyme involved in the reduction of various disulfide compounds, is higher in younger leaves than in older ones. A similar pattern was obtained in the activity or thioredoxin, a small protein known as a cofactor of ribonucleotide reductase and a regulator of photosynthesis. Activity of glutathione rednctase is also higher In the younger leaves. Malate dehydrogenase activity remains relatively constant during the development of Arabidopsis leaves. The results offer preliminary information for further approach to elucidate the mechanism of growth-dependent variations of these enzymes. Keywords: Arabidopsilf thaliana, Glutathione reductase. Phenylalanine ammonia-lyase, Thioltransferase. Thioredoxin,