Purification and characterization of lens specific calpain (Lp82) from bovine lens.
Ubiquitous type m-calpain and lens specific Lp82 calpain were separated and partially purified from fetal bovine lens and the enzymatic characteristics were compared. Lens m-calpain required 200 microM calcium for 1/2 maximal activity, while Lp82 required 30 microM. Both types of calpains were inhibited by 0.1 mM E64, and 5 mM iodoacetamide, but not by 1 mM phenylmethylsulfonyl fluoride. Lp82 was insensitive to 1 microM calpastatin peptide while m-calpain was effectively inhibited. In the presence of calcium, m-calpain lost most of its activity within 2 hr, while Lp82 was continually active for 18 hr. Both calpains cleaved the natural substrates betaA3 and alphaB crystallins in a similar manner. However, incubation of alphaA crystallin with m-calpain removed ten amino acid residues from its C-terminus, while incubation with Lp82 removed only five residues. The latter truncation product of alphaA was also found in vivo. These data suggested that Lp82 may have a more important role than m-calpain in modification of crystallins during lens maturation.
Ueda
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Department of Animal Science, Oregon State University, Corvallis, OR 97331, USA.
McCormack
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Shearer
T R
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David
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LL
D000818:Animals; D002135:Calcium-Binding Proteins / Q000502:physiology; D002154:Calpain / Q000302:isolation & purification* / Q000502:physiology; D002417:Cattle; D002853:Chromatography, Liquid / Q000379:methods; D003459:Crystallins / Q000737:chemistry / Q000502:physiology; D004591:Electrophoresis, Polyacrylamide Gel; D006863:Hydrogen-Ion Concentration; D007091:Image Processing, Computer-Assisted / Q000379:methods; D007124:Immunoenzyme Techniques; D007908:Lens, Crystalline / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods; D013997:Time Factors
D002135:Calcium-Binding Proteins; D003459:Crystallins; C033668:calpastatin; D002154:Calpain; C118624:calpain Lp82