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Human lens carbonic anhydrases. Purification and properties
1Department of Ophthalmology, Akademiska Sjukhuset, University of Uppsala, Sweden. Per.Wistrand@medfarm.uu.se
Acta Ophthalmologica Scandinavica
|November 7, 1999
Summary
Human lenses contain carbonic anhydrase (CA) isozymes CAI, II, and III in the cytoplasm and CAIV at plasma membranes. These isozymes likely facilitate CO2 transport and ion transport, without causing cataracts.
Area of Science:
- Ophthalmology
- Biochemistry
- Enzymology
Background:
- Carbonic anhydrase (CA) is crucial for physiological processes.
- Understanding CA isozyme distribution in the human lens is important for ocular health.
Purpose of the Study:
- To isolate and characterize carbonic anhydrase (CA) isozymes within human lenses.
- To determine the specific roles and locations of these CA isozymes.
Main Methods:
- Affinity chromatography was employed for CA isozyme separation.
- Immunosorbent assays monitored CA isozyme isolation.
- Amino acid analysis characterized the antigenic CAII.
- Catalytic activity and inhibition sensitivity assays were performed on soluble and membrane-bound CA isozymes.
Main Results:
- Human lenses contain CA isozymes CAI, II, and III (0.25, 9, and 2 microg/g wet weight, respectively).
- The majority of CA catalytic activity is attributed to CAII.
- Plasma membranes exhibit CA activity, inhibited similarly to the membrane-bound isozyme CAIV.
Conclusions:
- CA activity in the human lens originates from cytoplasmic CAI, II, and III, and membrane-bound CAIV.
- CA isozymes likely facilitate CO2 transport, similar to erythrocyte function.
- CAII and CAIV may play roles in translenticular ion transport.
- Chronic CA inhibitor use does not appear to induce cataract formation.