Abstract
The transferase-type of xyloglucan endotransglucosylasee (XETs) in the primary wall has been proposed to form an enzyme-acceptor complex as well as an enzyme-donor complex at the onset of cleavage of the glucan backbone. When whole xyloglucan was added exogenously to pea stem, XET bound to the non-reducing end of xyloglucan, forming an enzyme-acceptor complex in the cell walls. This complex could catch the internal region of exogenous whole xyloglucan, cleave it and transfer this newly generated reducing end to the non-reducing end of the endogenous one. Thus, the xyloglucan in the wall becomes a larger molecule during endotransglucosylation. To identify and define the reaction mechanism of XETs, we purified XET isozymes from pea epicotyls. XETs were purified by sequential lectin affinity chromatography, gel permeation and cation exchange chromatography, and chromatofocusing. Four isozymes were identified as XET.
