Abstract
The discovery of the active group of the hydrogen-transferring enzymes - nicotinamide -for which Otto Warburg was nominated by the Nobel Committee "for a prize for the second time in 1944, when he again was found to deserve the honor", has had a profound influence on all of biochemistry. The present paper describes a fundamental inhibition of intracellular tumor metabolism produced by reduced diphosphopyridine nucleotide (DPNH2) added extracellulary.