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Inhibition of the Pasteur Effect in Yeast by Tumor Extracts and Differences in Lability of Sulfur in Normal and Tumor Tissues^*

( Institute for Enzyme Research and the Department of Biochemistry, University of Wisconsin, Madison 6, Wis.)

1. Carbon tetrachloride extracts from mild alkali-treated acetone powders of a variety of rat and human tumors inhibited the Pasteur effect in baker's yeast. Complete inhibition was obtained with extracts containing dry matter ranging from 5 to 15 µg/ml of yeast fermentation assay system. Similar extracts from normal tissues, except testis and semen, were inactive. Embryonic tissue extracts showed activity only at high levels.

2. After the active principle, which was originally discovered in mammalian spermatozoa (12), had been identified as elemental sulfur,¹ the acetone powders of normal and malignant tissues were analyzed for total sulfur. Total sulfur content of rat tumors (Flexner-Jobling, Walker 256, and primary hepatoma) were slightly higher than that of rat muscle; the values for normal liver and hepatoma were, however, identical.

3. In view of the greater lability of sulfur in tumor, a structural difference between the sulfurcontaining proteins of normal and tumor tissues is postulated. This difference was relative in mitochondrial, microsomal, and supernatant fractions and absolute in the nuclear fractions of the respective tissues.

^* Supported by a grant from the American Cancer Society, on recommendation by the Committee on Growth of the National Research Council, and by the Brittingham Trust Fund. A preliminary report was presented before the American Association for Cancer Research (Cancer Research, 11:251, 1951).

Received 12/12/51.