ENZYMATIC-HYDROLYSIS OF 4-O AND 6-O-INDOL-3-YLACETYL-BETA-D-GLUCOSE IN PLANT-TISSUES

The activity of the enzyme catalyzing the hydrolysis of IAA glucose co njugates has been studied in vegetative tissues of plants. We have dem onstrated the presence of this enzyme in sprouts of oat (Avena sativa L.), potato tubers (Solanum tuberosum L.) and sprouts of bean (Phaseol us vulgaris L.). 4-O and 6-O-IAA glucose esters caused the stimulation of Avena coleoptiles growth in elongation tests. This fact points to enzymatic hydrolysis of IAGlucose isomers as a process yielding free I AA and glucose. We have also found activity of two enzymes catalyzing the hydrolysis of IAA glucose esters in potato tubers. The enzyme spec ifically hydrolysing 6-O(4-O)-IAGlucose was partially purified using f ractionation by PEG 6000, followed by ion-exchange, hydrophobic intera ction and gel filtration chromatography. The enzyme has a molecular we ight of 32 kDa, it shows a very similar activity over the range pH 6 - 9. The affinity of the enzyme for 6-O(4-O)-IAGlucose is in milimolar range, K(m) = 10 milimolar. The presence of enzymes hydrolysing of IAA glucose conjugates in storage plant tissues may have physiological si gnificance in regulating of free auxin level.