Mechanism of Alanine Hyperproduction by Arthrobacter oxydans HAP-1: Metabolic Shift to Fermentation under Nongrowth Aerobic Conditions

Arthrobacter oxydans HAP-1 hyperproduces dl-alanine in a non-growth-associated manner. We found that decreased activities of pyruvate dehydrogenase and of the enzyme catalyzing NADH oxidation in the stationary phase are paralleled by a shift of pyruvate metabolism to alanine synthesis by l-alanine dehydrogenase. We propose that this enzyme functions as an electron sink even under aerobic conditions.