Comparison of Tryptophan Metabolism in Vivo and in Isolated Hepatocytes from Vitamin B6 Deficient Mice

摘要: Tryptophan dioxygenase meets the traditional criteria for rate-limiting enzyme of kynurenine pathway tryptophan metabolism. From concentrations substrates in liver and published values Km Vmax (Bender et al., 1975; Bender McCreanor, 1985; Takikawa 1986), steady-state rates activity can be calculated. As shown Table 1, such calculations show that has lowest under basal conditions. Furthermore, it is regulated by a variety mechanisms, including: induction mRNA synthesis glucocorticoid hormones; increased translation glucagon; stabilization protein against catabolism both heme cofactor; feedback inhibition repression reduced nicotinamide nucleotide coenzymes NADH NADPH.