EFFECT OF SHEARING FORCES ON THE CATALYTIC ACTIVITY OF UREASE.

It is shown by a combination of kinetic and analytical measurements that urease is permanently inactivated by shearing forces only if moieties which destroy the sulfhydryl group on cysteine residues are present and efficacious and urease has formed high molecular weight aggregates. Evidence support this is presented plus additional experiments which indicate that the irreversible inactivation that we have observed during shearing is a shear promoted metal ion catalyzed oxidation of an essential sulf-hydril group(s) on urease oligomers. At sufficiently high shear stresses, a reversible inactivation is also observed which the authors tentatively attribute to a reversible shear induced conformation change in the aggregated urease species.