Immunochemical characterization and quantification of larval brine shrimp malate dehydrogenase
Abstract
The cytosolic malate dehydrogenase (s‐MDH) from larval brine shrimp has been immunochemically characterized by quantitative rocket immunoelectrophoresis (IEP) and antibody catalytic inhibition studies. Monospecific rabbit antiserum produced against purified naupliar s‐MDH was used for rocket IEP as a quantitative assay for the cytoplasmic isozyme. Since cross‐reactivity was not observed against the mitochondrial MDH (m‐MDH), the assay allows specific measurement of the s‐MDH in crude naupliar supernatants in the presence of contaminating m‐MDH. The assay has a sensitivity of approximately 100 nanograms s‐MDH protein using either purified enzyme solutions or crude supernatant preparations. Catalytic inhibition studies using the monospecific antiserum gave 85% inhibition of s‐MDH but did not give significant inhibition of the m‐MDH. Lack of complete s‐MDH inhibition by the antiserum suggests a difference between the enzyme active site and immunological binding site. Although the antiserum was produced against s‐MDH from nauplii of the San Francisco Bay population, the antiserum inhibits equally well the s‐MDH of Great Salt Lake (Utah) nauplii, indicating little if any structural difference in the immunological sites of the s‐MDHs from these two geographical sources. Porcine (s‐ and m‐MDH), bovine (m‐MDH), and pigeon (m‐MDH) were also tried as antigens against the brine shrimp s‐MDH antiserum, but antigen‐antibody reactivity was not observed during rocket IEP or catalytic inhibition experiments. Copyright © 1982 Wiley‐Liss, Inc., A Wiley Company