Hydrogen sulfide oxidation by abundant nonhemoglobin heme compounds in marine invertebrates from sulfide‐rich habitats

Publisher Website
Google Scholar
Abstract
Several animals from hydrogen sulfide‐rich marine habitats were found to contain unusual heme compounds (hematins) at levels of up to 10 mM; these hematins catalyzed the oxidation of sulfide and may protect the animals from sulfide poisoning. Freshly captured specimens of the echiuran worm Urechis caupo contained 0–10 mM hematin in their coelomic fluid. This hematin was present within coelomocytes in addition to 0.5–2 mM hemoglobin present in these cells as a functional oxygen‐binding hemoprotein. The hematin was present in granules, and was not associated with a globin, cytochrome, or other protein known to have a heme prosthetic group. The hematin catalyzed oxidation of hydrogen sulfide. Further studies revealed that similar hematins were present in gill tissues of bivalve molluscs, which harbor vast numbers of endosymbiotic sulfur bacteria. Hematin was found at 1.0 mM, in addition to 0.1 mM hemoglobin, in the gill tissue of the clam Solemya reidi. Hematin was also found at 1–2 mM in gill tissue of two other clams, Calyptogena magnifica and Lucinoma annulata, in addition to < 0.4 mM hemoglobin. These clam hematins also appeared to be catalysts of sulfide oxidation.