Plant endo-1,4-beta-D-glucanases: structure, properties, and physiological function
1994
Brummell, D.A. | Lashbrook, C.C. | Bennett, A.B.
Multiple genes encoding distinct endo-1,4-beta-D-glucanases have been characterized in plants. The enzymes are of approximately 50 to 70 kDa, and possess discrete amino acid domains that are conserved with microbial cellulases of the E2 subgroup. Low levels of extractable endo-1,4-beta-D-glucanase activity have been found in virtually all plant organs, with higher levels being associated with certain developmental processes which involve modifications in cell wall structure, such as cell elongation, leaf abscission and fruit ripening. In many cases, the developmentally regulated changes in Endo-1,4-beta-D-glucanase activity have been shown to result from hormone-mediated changes in gene expression. Activities of an auxin-induced, ethylene-antagonized endo-1,4-beta-D-glucanase have been correlated with the cell expansion process, and activities of an ethylene-induced, auxin-antagonized type have been correlated with organ abscission and fruit ripening. The enzymes that have been cloned possess predicted signal sequences, and several have been immunolocalized to the cell wall where they presumably act against cell wall polysaccharides. Their precise in vivo substrates have not yet been established, although they do not appear capable of acting alone on native crystalline cellulose. It is possible that the multiplicity of genes and their diverse pattern of developmental regulation contributes to the disassembly of distinct components of the plant cell wall.
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