Chemical modificiation of collagen and the effects on enzyme-binding: mechanistic considerations

The effect of structural modification on the enzyme-binding capacity of collagen has been studied using beta-galactosidase (E. coli K12) immobilized to collagen membrane by the impregnation procedure. The apparent steady-state activities of the resultant collagen-enzyme complexes were determined as a means of evaluating the enzyme-binding capacity of the modified collagen. In addition, the amount of enzymic protein bound to the collagen support was determined by the tryptophan content of the complex. The tertiary structure of the collage matrix was modified by cross-linking with the difunctional reagent, glutaraldehyde, and by aging in the dry state. Such structural modifications were found to markedly reduce the enzyme (beta-galactosidase) binding capacity of collagen films. The enzyme-binding capacity of the crosslinked collagen membrane was completely restored by proteolytic enzyme treatment of the aged film but only partly so for the glutaraldehyde treated films. Proteolytic enzymes used to treat a dispersion of collagen microfibrils prior to casting into a membrane also resulted in an increase in enzyme-binding. The effect of structural modification of collagen on enzyme-binding and the locus of enzyme attachment are discussed.