Aerobic glycolysis of bone and cartilage: the possible involvement of fatty acid oxidation.

The apparent paradox of aerobic glycolysis has been investigated in bone and in cartilage. A new cytochemical procedure for hydroxyacyl dehydrogenase (HOAD) activity showed that the maximal activity of this enzyme in both tissues was equivalent to the maximal activity of glyceraldehyde 3-phosphate dehydrogenase (GAPD). The sum of these activities gave a measure of the maximum amount of acetyl-coenzyme A that could be produced. In these tissues, but not in liver which does not exhibit aerobic glycolysis, this summed value exceeded the maximal activity of succinate dehydrogenase (SDH). Consequently, it suggested that where fatty acid oxidation is sufficient to supply all the acetyl-coenzyme A required for the Krebs' cycle, that derived from fatty acid oxidation may inhibit pyruvate dehydrogenase causing accumulation of pyruvate which must be converted to lactate if pentose-shunt activity is to be maintained.