ABSTRACT
Figure 16.1 0 Catecholamin e biosynthesi s an d metabolism . M A O , monoamin e oxidase ; COMT, catecholamine-O-methyltransferase ; SAM , 5-adenosylmethionine .
The secretio n o f epinephrin e b y th e adrena l medull a i s controlle d directl y
by nerv e impulse s an d als o b y th e othe r stres s hormones , namely , corti -
costeroids. Thi s i s illustrate d i n F igur e 16.11 . Nerv e impulse s hav e a majo r
stimulatory effec t o n tyrosin e an d dopamin e hydroxylases , wherea s gluco -
corticoids hav e a majo r effec t o n phenylethanolamin e meth y transferase. Ty -
rosine hydroxylas e i s considere d th e rate-controllin g enzyme i n the biosynthesi s
Adrenal glan d
Figure 16.1 1 Contro l o f catecholamin e biosynthesi s i n th e adrena l medulla . T H , tyrosine hydroxylase ; D B H , dopamine hydroxylase ; PNMT , phenylethanolamin e methyl - transferase; A C T H , adrenocorticotropi c hormone. Th e heav y arrow s indicat e major site s of regulation . (Reproduced b y permission from Axelrod , J . Reisine TD . Stres s hormones : their interaction and regulation . Science 224:452-459, 1984. )
of catecholamines . I t i s a n iron-containin g enzyme , an d a n unusua l redo x
cofactor, tetrahydrobiopterin , i s require d in thi s reaction . It s structure and prop -
erties ar e discusse d i n Chapte r 20.
