Abstract
Xyloglucan endotransglucosylases (XETs) in the cell wall catalyze the transfer of a portion from a donor xyloglucan to acceptor xyloglucan molecule, and are considered to contribute to plant cell growth. We purified XET isoenzymes from growing pea stems. Kinetic studies using whole xyloglucans as a donor and xyloglucan heptasaccharide (XXXG) as an acceptor support a sequential mechanism for the enzymes. We suggest that XETs occur as an enzyme-acceptor complex as well as an enzyme-donor complex in the cell wall. In the transverse sections of pea stems, the incorporation of fluorescent XXXG was observed at the epidermis of the third internode, and that of fluorescent whole xyloglucan was in the vascular bundles of first and second internodes. The results showed that XET-donor and XET-acceptor complexes were differently localized in pea stems.
