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A Relation between Pyridine Nucleotide-dependent Dehydrogenase Activity and Nicotinamide Adenine Dinucleotide Glycohydrolase in Ehrlich Ascites Tumor Cells

Division of Biochemistry, Sloan-Kettering Institute for Cancer Research, New York, New York 10021

The stability of glyceraldehyde 3-phosphate dehydrogenase, malic dehydrogenase, glutamic dehydrogenase, -glycerophosphate dehydrogenase (NAD⁺ - specific enzymes), as well as glucose 6-phosphate dehydrogenase and 6-phosphogluconic dehydrogenase (NADP⁺ - specific enzymes) was determined in a 105,000 x g supernatant solution of an Ehrlich ascites cell homogenate during incubation at 37°. The percentages of activity lost by each enzyme in 1 hr were 72, 4, 29, 33, 38, and 3, respectively. Added NAD glycohydrolase increased the loss of glyceraldehyde 3-phosphate dehydrogenase activity to 93% and the loss of glutamic dehydrogenase activity to 46%. Malic dehydrogenase and -glycerophosphate dehydrogenase were unaffected.

Glucose 6-phosphate dehydrogenase and 6-phosphogluconic dehydrogenase in the supernatant solution or as purified enzymes were not affected by added NAD glycohydrolase but lost significant amounts of activity when incubated in the simultaneous presence of NAD glycohydrolase and NADP⁺.

Glyceraldehyde 3-phosphate dehydrogenase from Ehrlich ascites cells and from rabbit muscle (crystalline) were rapidly inactivated by a component of an ascites cell extract in the presence of NAD glycohydrolase. Complete protection against such inactivation was conferred by excess NAD⁺ and by nicotinamide. The inactivating factor present in the tumor cell extract was heat labile and nondialyzable.

Ascites cells treated with 1,3-bis(2-chloroethyl)-1-nitrosourea had 6 times higher NAD glycohydrolase than controls and had significantly decreased levels in NAD⁺-specific dehydrogenases. Increased intracellular NAD glycohydrolase activity may result in a decrease in the activity of those enzymes which require NAD⁺ or NADP⁺ for structural stability, for protection against proteolytic inactivation, or are inhibited by the end products of NAD⁺ or NADP⁺ hydrolysis.

Received 4/11/69. Accepted 6/ 5/69.