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Clinical Chemistry, Vol 36, 59-64, Copyright © 1990 by American Association for Clinical Chemistry
RN Weijers, R de Bruijn, J Mulder and H Kruijswijk
Department of Clinical Chemistry, Onze Lieve Vrouwe Gasthuis, Amsterdam, The Netherlands.
Lactate dehydrogenase (L-lactate:NAD+ oxidoreductase, EC 1.1.1.27) isoenzyme-3 (LD-3) has been isolated in milligram quantities from human erythrocytes. Using an improved procedure--which involves complete hemolysis of the erythrocytes, diethylaminoethyl (DEAE)-Sephacel column chromatography, and 5'-AMP-Sepharose 4B affinity chromatography--we obtained 23,000-fold purified isoenzyme from the crude hemolysate (overall yield about 90%). The final product was homogeneous on polyacrylamide disc gel electrophoresis and had a specific activity of about 435 kU/g. Its amino acid composition is presented. With the eventual aim to make visible and isolate IgA kappa antibody-secreting B lymphocytes, we developed reproducible methods for preparing fluorescein isothiocyanate isomer-1-conjugated LD-3 with a fluorescein/LD-3 molar ratio between 1.3 and 3.3, and biotinylated LD-3 with a biotin/LD-3 molar ratio between 1.3 and 2.5. In evaluating the stability of these two conjugates, we determined that they still can react with IgA kappa to form the IgA kappa (LD-3)2 complex.
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