A glyceraldehyde 3-phosphate dehydrogenase-inactivating factor has been isolated from the 105,000 × g supernatant solution of Ehrlich ascites tumor cells. This factor was purified 35-fold by steps that include the following: (NH4)2SO4 fractionation; freezing, thawing, and dialysis at 37°; and, finally, filtration chromatography through Sephadex G-100. The factor had a maximum absorption at 280 mµ, was not dialyzable, was heat labile, and could be precipitated by 10% trichloroacetic acid. The factor had no detectable proteolytic activity with denatured hemoglobin or α-benzoyl-dl-arginine-p-nitroanilide and was not affected by N-ethylmaleimide or soybean trypsin inhibitor. Excess NAD+ was required for complete protection of purified Ehrlich ascites tumor glyceraldehyde 3-phosphate dehydrogenase from inactivation by factor. Glyceraldehyde 3-phosphate dehydrogenase purified from rabbit muscle, Ehrlich ascites cells, mouse muscle, and yeast showed significantly different sensitivities to inactivation by factor.

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This work was supported by National Cancer Institute Grant CA 08748 and American Cancer Society Grant T-431M.

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