NADP+ reduction by human lymphocytes.
The hexose monophosphate shunt (HMPS) is known to be responsible for the reduction of NADP+ by lymphocytes. We tried to find other enzymatic systems that might provide the lymphocytes with NADPH. By measuring the absorbance at 340 nm we noted that the addition of NADP+ to a preparation of disrupted lymphocytes resulted in the formation of NADPH at a rate of 4 nmol/10(6) cells per min. This phenomenon could not be changed by negative feedback inhibition of HMPS, and could not be attributed to the low concentration of glucose, glucose-6-phosphate (G-6-P) and isocitrate found in the cell preparation (NADP(+)-dependent isocitrate dehydrogenase in addition to HMPS NADP+ reducing enzymes was found to be present in lymphocytes). Because of the activity of a NADP(+)-dependent lactate dehydrogenase, pyruvate oxidized the NADPH as it was being formed. Here we demonstrate the presence of an unknown NADP+ reducer in lymphocytes which seems to play an additional role to HMPS in NADP+ reduction by lymphocytes. NADP(+)-dependent lactate dehydrogenase may play a role in regulating the NADP+/NADPH ratio.
Klein
A
A
Department of Clinical Biochemistry, Sunnybrook Medical Centre, University of Toronto, Ontario, Canada.
Chan
A W
AW
Caplan
B U
BU
Malin
A
A
D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008214:Lymphocytes / Q000201:enzymology*; D009249:NADP / Q000378:metabolism*; D010084:Oxidation-Reduction; D010427:Pentose Phosphate Pathway / Q000502:physiology; D011773:Pyruvates / Q000494:pharmacology; D019289:Pyruvic Acid
D011773:Pyruvates; D009249:NADP; D019289:Pyruvic Acid; D007770:L-Lactate Dehydrogenase