ABSTRACT
Tryptophan, a n essentia l amin o acid , give s ris e t o glucogeni c an d ketogeni c en d
products, a s wel l a s a numbe r o f physiologicall y importan t nitrogenou s com -
pounds , suc h a s serotoni n an d N A D + . Th e fate o f tryptopha n i s summarize d i n
Figure 20.21 . Catabolism o f tryptopha n ca n b e divide d int o th e serotoni n an d 3-hy -
droxyanthranilic aci d pathways , th e latte r bein g b y fa r th e mor e prevalent . I t
may lea d t o th e formatio n o f N A D + o r t o a-ketoadipi c acid . O n l y about 3 % o f 3 -
Figure 20.2 1 Catabolis m o f tryptopha n b y th e serotoni n an d 3-hydroxyanthranilat e pathways. B v B 2 , and B 6 indicate the participatio n of coenzymes derive d from th e respec - tive vitamins . Notice tha t tryptopha n i s glucogeni c an d ketogenic , becaus e i t produce s alanine o n th e on e hand , an d acetoacetyl-Co A o n the other .
