Alpha‐crystallin acting as a molecular chaperone protects catalase against steroid‐induced inactivation

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Abstract
A link between corticosteroid therapy and the development of cataract has been known for many years. However, the precise underlying molecular mechanism of pathology has not been characterised, although a role for direct deleterious interactions between corticosteroids and lenticular proteins has been investigated. α‐Crystallin is a major lens protein that has exhibited chaperone properties in vitro. Catalase is a ubiquitous enzyme that is an important scavenger of hydrogen peroxide in vivo. The corticosteroid prednisolone‐21‐hemisuccinate was found to inactivate bovine liver catalase, in vitro in a progressive manner. Coincubation of α‐crystallin with catalase in a 1:2 molar ratio (one α‐crystallin to two catalase molecules) fully protected against this inactivation. The protection was specific. Aspirin‐like analgesics, putative anti‐cataract drugs offered no such protection.