Trace Elements and Sulfhydryl Groups

Prevention op Decline of a-KBTOOLUTARATE Oxidation by Reduced Glutathione and Dimercaptopropanol 

In Vilro Effect of Protecting Agents on Free Sulfmydryl Groups 

Protection by Vitamin E and Other Quinonoid Compounds A. Tocopheeols and Derivatives 

The potencies of various tocopherols, K vitamins, ubiquinones, and similar substances in the prevention of respiratory decline have been assayed by supplementation of graded dose levels to the whole homogenate system. For each dose level, averages of at least four experiments were established. From the dose-response curves, the 50 % effective dose (EDbo) was derived. The EDso for df-a-tocopherol was found to be 1.1 ng per 3 ml of medium containing 50 mg of homogenized liver (Table VII). A comparison of the potencies of a-, /3-, 7-, and 5-tocopherols gave the same relative order of activity as the resorption sterility assay for vitamin E. df-a-To-copheryl acetate demonstrated only 3 % of the activity of the free vitamin. a-Tocopherylquinone was about 10% as active as tocopherol itself. The Simon metabolite (Simon et al., 1956) (Fig. 4) showed 40% of the activity of di-a-tocopherol, in spite of the fact that it was supplied in the quinone form. 

When tested under identical conditions, some synthetic antioxidants are more potent than tocopherol. For example, the approximate EDso for amylhydroquinone is 0.5, for methylene blue 0.3, and for DPPD (N,N -diphenyl-p-phenylenediamine) 0.03 ixg (Schwarz and Lee, 1961). We have postulated since 1956 that tocopherol may be converted into an active form before exerting its catalytic metabolic effect (Rodnan et al., 1956). In this regard it is noteworthy that a synthetic preparation of an a-tocoph- 

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K. Schwarz Vitamin E, Trace Elements and Sulfhydryl Groups in Respiratory... 

VITAMIN E, TRACE ELEMENTS, AND SULFHYDRYL GROUPS 473 TABLE IV Prevention op Decline Due to Arsbnite and Cd" by a-TocoPHEROL ... 

It is imaginable, in view of the significance of trace elements for the maintenance of tertiary structures and active sites of enzyme molecules, that the juncture between sulfhydryl groups and the active quinones is formed through coordination with a trace metal, for instance, Mn. In this currently, purely hypothetical case the various categories effective in our system, namely, sulfhydryl groups, trace elements, and quinones, would function jointly at a common site of action. 

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