Bovine lens aldehyde dehydrogenase. Purification and preliminary characterization

Abstract

Cytoplasmic aldehyde dehydrogenase from bovine lens was purified to apparent homogeneity by using ion-exchange and affinity chromatography. Sedimentation-equilibrium ultracentrifugation, gel-filtration chromatography and sodium dodecyl sulfate/polyacrylamide-gel electrophoresis show that the enzyme is a dimer of MW 114,000, with subunits of MW 57,000. The enzyme does not dissociate into monomers in the presence of Ca2+ or Mg2+. The enzyme has a PI [isoelectric point] of 5.0, an activation energy of 35.1 kJ/mmol and a pK value of 8.6 with acetaldehyde as substrate. The enzyme is a prolate ellipsoid with a Stokes radius of 4 nm. Progesterone, deoxycorticosterone and chlorpropamide inhibited enzyme activity, and this inhibition may play a role in cataract formation in patients maintained on systemic corticosteroids and in tablet-dependent diabetics.