120] Picolinic car☐ylase in reference to NAD biosynthesis

Abstract

Publisher Summary This chapter describes the synthesis of the enzyme picolinic carboxylase in reference to nicotinamide adenine dinucleotide (NAD) biosynthesis. Tryptophan serves as a precursor to NAD in animals and certain microorganisms. The liver and kidney are responsible for this conversion. The amount of NAD synthesized from tryptophan is inversely related to the activity of picolinic carboxylase. The activity of picolinic carboxylase varies with various hormonal conditions. In the diabetic rat, the activity increases markedly with a concomitant decrease in the formation of NAD from tryptophan, and eventually in the urinary excretion of N’ -methylnicotinamide. A method to measure the formation of pyridine nucleotides from tryptophan and its metabolites with special reference to its relation to picolinic carboxylase or glutarate pathway is discussed in the chapter. All measurements are performed with crude extracts of the liver and kidney in assay in vitro . Experiments may be carried out in vivo to ascertain whether or not the activity of picolinic carboxylase is parallel with that of the glutarate pathway and is inversely related to the amount of NAD synthesized from tryptophan.