Action of shear on enzymes: Studies with catalase and urease

Abstract

SummaryIntermittent shear was applied to approximately 1 mg/ml solutions of bovine liver catalase in a coaxial cylindrical viscometer at temperatures from 20 to 60°C and shear rates up to 683 sec-I. The viscometer was sealed to prevent evaporation. Up to 40°C there were no activity losses during 3 hr total shearing. Above 40°C shearing reduced losses due to thermal inactivation, possibly by interfering with precipitation. At 3440 sec-l and 40°C fine precipitates formed but little activity was lost. No activity losses were found with experimentai conditions under which Taylor vortexing occurred, nor when shear stresses were increased up 57 times by adding glycerol to raise the viscosity. There were no significant losses in a capillary rheometer at shear rates up to 106 sec-*. When low concentration (6 pgiml) catalase solutions were sheared there was little loss in sealed systems, but there were losses in "open" systems even in low-temperature nonshear experiments. Although there were no losses with 1 mg/ml solutions, 6 pgiml catalase solutions from an alternative source did lose activity in sealed systems but much less than expected from previously published work. Approximately 1 mg/ml jack bean urease solutions were sheared in the sealed system at 23°C and 683 sec-I for 3 hr. N o losses were found. No evidence of temporary or permanent inactivation was found with 28 pgiml solutions sheared in the presence of urea. Shear forces alone were not found to be as effective in causing enzyme inactivation as is generally believed and alternative mechanisms for damage are discussed.

Factors influencing antibody stability at solid–liquid interfaces in a high shear environment

“…This work supports previous conclusions that some proteins are more susceptible to interfacial shear effects than others, 12,14,15 and so for processing considerations each protein would need to be treated on a case by case basis.…”

“…Additionally, it was clear from the literature that these interfacial effects were damaging to some proteins but not others. 12,14,15 Therefore, to expand the scope of the study, the monomer reduction rates of ovalbumin, lysozyme, a-chymotrypsin, and hemoglobin were determined under high shear conditions.…”

Development of an ultrahigh‐temperature process for the enzymatic hydrolysis of lactose. III. Utilization of two thermostable β‐glycosidases in a continuous ultrafiltration membrane reactor and galacto‐oligosaccharide formation under steady‐state conditions

“…Shearing forces are probably not solely responsible for the observed protein denaturation, and other eects connected with a high pumping velocity may be as important, eventually including inactivation at the gas-liquid interface or due to local heating (cf. Narendranathan and Dunhill, 1982;Thomas and Dunhill, 1979). By decreasing the recirculation rate from 5 min )1 to 0.5 min )1 , it was possible to signi®cantly increase the half-life times of the enzymes while at the same time, membrane fouling did not prevent long-term operation of the CSTR.…”

Protein aggregation: Pathways, induction factors and analysis

“…13 Although agitation stress is sometimes referred to as shear stress, several studies [59][60][61] suggest that shear alone does not cause protein aggregation. Agitation has been described to potentially cause cavitation 62 where cavitation is described as the rapid formation of voids or bubbles within the liquid which rapidly collapse thus producing shock waves, highly turbulent flow conditions, extreme pressures and temperature which may result in the generation of hydroxyl and hydrogen radicals thus leading to the formation of protein aggregates. 63,64 Mechanical stress testing in lab experiments could be performed under controlled conditions using, for example, horizontal or vertical shakers, 13,18 stirred reactors 65 and pumps, 11,66 rheometers such as concentric-cylinder shear devices or cone-plate, rotating-disk reactors, 57,58 to mimic ''real-life'' mechanical stresses which proteins may experience.…”