The Prosthetic Group of Sulfhemoglobin by Felix Iiaurowitz*

Treatment of hemoglobin with H&S and 02 gives rise to the formation of a green pigment, sulfhemoglobin. In contradistinction to the transformation of hemoglobin into HbOz, HbCO, Meth-Hb, and other hemoglobin derivatives the transformation into sulfhemoglobin is not reversible. The nature of this reaction is as yet unknown (1). An attempt.was made therefore to isolate the prosthetic group of sulfhemoglobin and to clear up its constitution. Difficulties arose first of all in preparing pure sulfhemoglobin. The typical absorption band in the red region of the spectrum after having reached a certain intensity showed a gradual decrease of its extinction during prolonged treatment with II&S and 02 (Fig. 1). Probably the nascent sulfhemoglobin is autocatalytitally destroyed later on by traces of HzOz, the formation of which from HzS and 02 has been proved (2, 3). Contrary to hemoglobin and oxyhemoglobin, sulfhemoglobin is not split into a hemin and globin by the action of dilute acids. Keither boiling acetic acid and NaCl (Schalfejef) nor oxalic acid and acetone (4) cause the formation of hemin. We treated sulfhemoglobin therefore with pepsin and HCZ, a method used first by von Zeynek (5) for the splitting of Hb. By repeated digestion with pepsin the bulk of the protein compound was split off. But contrary to the results with oxyhemoglobin 5 to IO per cent of the globin adhered to the pigment. Instead of pure hemin (6) a brown hemin-protein compound was obtained. It will be designated in