Concanavalin A: a useful ligand for glycoenzyme immobilization--a review

Concanavalin A is finding increasing applications as a useful ligand in glycoenzyme immobilization. An attempt therefore, has been made to summarize the work available in the area. Glycoenzymes that are recalcitrant to immobilization procedures involving covalent coupling to solid supports can be immobilized in high yields by binding to matrices precoupled with concanavalin A. In addition, glycoenzymes associated with concanavalin A matrices usually exhibit high retention of activity and enhanced stability against various forms of inactivation. Binding of the glycoenzymes on the concanavalin A supports, being noncovalent, can be reversed by incubating the preparation with a high concentration of sugars/glycosides or at acidic pH. The association can be, however, rendered covalent by crosslinking the preparations with bifunctional reagents like glutaraldehyde. Crosslinking may be accompanied by further increase in stability, albeit at the expense of the loss of some enzyme activity. Several laboratory-size reactors containing concanavalin A matrix-bound glycoenzyme have been successfully operated for reasonably long durations with only small losses in catalytic activity. Insoluble glycoenzyme preparation can also be obtained by precipitating them from solution as concanavalin A complexes. Such complexes have small particle dimensions but can be successfully used in column reactors after a subsequent immobilization step. Insoluble concanavalin A-flocculates containing various microorganisms and glycoenzymes that successfully carry out multistep transformations have also been obtained by several investigators.