The Promoting Effect of Aluminum, Chromium, and the Rare Earths in the Succinic Dehydrogenase-cytochrome System

In the course of an investigation on the succinic dehydrogenasecytochrome enzyme system, y-aluminum hydroxide was used in an attempt to isolate certain of its components. The inconsistency of the results and the increased total activity obtained by this procedure suggested that some important factor was introduced by this treatment. Studies with such a factor in view showed clearly that aluminum ion addition in very small concentrations accelerated the aerobic oxidation of succinate markedly. Subsequent studies showed that aluminum is not unique in this a.ccelerating property, but thaO it may be substituted by trivalent chromium and certain rare earths but not by ferric ion or by divalent ions. However, spectroscopic examination showed that of these metals only aluminum was present in the enzyme preparations in amounts sufficient to be of any significance. The following is a report of these &dings.