Abstract: The present invention relates to crosslinked protein crystals characterized by the ability to change from insoluble and stable form to soluble and active form upon a change in the environment of said crystals, said change being selected from the group consisting of change in temperature, change in pH, change in chemical composition, change from concentrate to dilute form, change in oxidation-reduction potential of the solution, change in the incident radiation, change in transition metal concentration, change in flouride concentration, change in free radical concentration, change in metal chelater concentration, change in shear force acting upon the crystals and combinations thereof. According to one embodiment of this invention, such crosslinked protein crystals are capable of releasing their protein activity at a controlled rate.

Abstract: Protein crystals crosslinked with a multifunctional crosslinking agent are produced that have the ability to change from an insoluble and stable form to a soluble and active form and to release protein activity at a controlled rate when a change in environment surrounding the crystals occurs. The change in environment may be a change in temperature, pH, chemical composition or shear force acting on the crystals, or a change from a concentrate to a dilute form, or a combination of the changes. The crosslinked protein crystals have a half-life activity under storage conditions greater than at least 2 times that of the soluble protein that is crystallized to form the crystals that are crosslinked, and under conditions of use have an activity similar to the soluble protein.