Oxidation of lactate to pyruvate requires which vitamin
Correct Answer: Niacin
Description: Oxidation of lactate to pyruvate require Niacin. Reduction of pyruvate to lactate Lactate, formed by the action of lactate dehydrogenase, is the final product of anaerobic glycolysis in eukaryotic cells (Figure 8.21). The formation of lactate is the major fate for pyruvate in lens and cornea of the eye, kidney medulla, testes, leukocytes and red blood cells because these are all poorly vascularized and/or lack mitochondria. 1. Lactate formation in muscle: In exercising skeletal muscle, NADH production (by glyceraldehyde 3-phosphate dehydrog ease and by the three NAD+-linked dehydrogenases of the citric acid cycle, see p. 112) exceeds the oxidative capacity of the respiratory chain. This results in an elevated NADH/NAD+ratio, ouring reduction of pyruvate to lactate. Therefore, during intense exercise, lactate accumulates in muscle, causing a drop in the intracellular pH, potentially resulting in cramps. Much of this lactate eventually diffuses into the bloodstream and can be used by the liver to make glucose (see p. 118). 2. Lactate consumption: The direction of the lactate dehydrogenase reaction depends on the relative intracellular concentrations of pyruvate and lactate, and on the ratio of NADH/NAD+in the cell. For example, in liver and hea, the ratio of NADH/NAD+is lower than in exercising muscle. These tissues oxidize lactate (obtained from the blood) to pyruvate. In the liver, pyruvate is either conveed to glucose by gluconeogenesis or oxidized in the TCA cycle. Hea muscle exclusively oxidizes lactate to CO2and H2O the citric acid cycle. Reference: Lippincott Textbook of Biochemistry pg no. 103
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