In differentiated tissues an increased conversion of glucose to lactate only takes place in the absence of oxygen (Pasteur effect). Around 1930, Otto Warburg showed that tumor cells produce lactate even in the presence of oxygen and he assumed that a defect in mitochondrial respiration in tumor cells was the reason for this observation. The conversion of glucose to lactate in the presence of oxygen has been termed aerobic glycolysis. Today we know that the lactate produced in tumor cells does not only derive from the conversion of glucose. Some of the lactate is produced by the degradation of the amino acids glutamine and serine to lactate, which has been termed glutaminolysis and serinolysis respectively. In tumor cells, lactate production in the presence of oxygen is caused by an isoenzyme shift in the glycolytic and glutaminolytic pathways. Glycolysis: main page |
