... picolinicacid (PA), quinolinic acid (QA) and NAD homeostasis. Indeed, the enzymestands at a branch point of the tryptophan to NAD pathway, and deter-mines the final fate of the amino acid, i.e. transformation ... profileand the associated variation in QA and PA levels [7],and other investigations have clearly demonstratedthat changes in ACMSD activity are readily reflectedby serum and tissue QA levels ... solution[18]. Therefore, the available structural data suggestthat the minimal functional unit in the ACMSDenzyme is a monomer. and the biological significance,if any, of the loose dimer observed in the...