Synergism between cucumber alpha-expansin, fungal endoglucanase and pectin lyase.
Several recombinant fungal enzymes (endoglucanase and pectinase) were studied for their interactions with alpha-expansin in cell wall extension and polysaccharide degradation. Both Cel12A and Cel5A were able to hydrolyze cellulose CMC-Na and mixed-linkage beta-glucan. In contrast to Cel5A, Cel12A could also hydrolyze xyloglucan and induce wall extension of cucumber hypocotyls in an in vitro assay. Combining alpha-expansin, even at high concentrations, with Cel12A did not enhance the maximum/final wall extension rate induced by Cel12A alone. These results strongly suggest that modification/degradation of the xyloglucan molecule/network is the key for cell wall extension, and alpha-expansin and Cel12A may share the same acting site in the substrate. Pectinase (Pel1, a pectin lyase) enhanced alpha-expansin-induced wall extension in a concentration-dependent manner, suggesting that the pectin network may normally regulate accessibility of expansin to the xyloglucan-cellulose complex. alpha-Expansin enhanced Cel12A's hydrolytic activity on cellulose CMC-Na but not on xyloglucan and beta-glucan. Expansin did not affect Cel5A's hydrolytic activity. Interestingly, expansin also enhanced Pel1's activity on degrading high esterified pectin. A potential explanation for why expansin could synergistically interact with only certain enzymes on specific polysaccharides is discussed. Additional results also suggested that cell wall swelling may not be a significant event during the action of expansin and hydrolases.
Wei
Wei
W
Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Science, Nanjing Normal University, Nanjing, PR China.
Yang
Chun
C
Luo
Jun
J
Lu
Changmei
C
Wu
Yajun
Y
Yuan
Sheng
S
D002480:Cellulase / Q000235:genetics / Q000378:metabolism*; D018553:Cucumis sativus / Q000235:genetics / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D005936:Glucans / Q000378:metabolism; D018546:Hypocotyl / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011133:Polysaccharide-Lyases / Q000235:genetics / Q000378:metabolism*; D011134:Polysaccharides / Q000378:metabolism; D014990:Xylans / Q000378:metabolism
D005656:Fungal Proteins; D005936:Glucans; D010940:Plant Proteins; D011134:Polysaccharides; D014990:Xylans; C095825:expansin protein, plant; C029353:xyloglucan; D002480:Cellulase; D011133:Polysaccharide-Lyases; C027349:pectin lyase