ABSTRACT
Figure 7.1 4 Structure s o f uroporphyrinogen s I an d I I I (structures I an d II ) and thei r oxidation products , uroporphyri n I and I I I (structure s I I I and IV) . (Reproduced b y permission fro m Die m K , Lentne r C . Scientifi c Tables. Basel : Ciba-Geigy , 1971 , pp . 355-362. )
ney failur e patients , henc e th e observe d anemi a conditio n i n suc h patients .
H e m e als o inhibit s th e translocatio n o f A L A - s y n t h a s e fro m th e cytoso l int o th e
mitochondria. Addit iona l control s includ e direc t allosteri c inhibitio n o f A L A-
synthase b y hem e an d th e fac t tha t amon g al l heme biosyntheti c enzymes , A L A -
synthase ha s th e highes t K m an d fo r tha t reaso n i s rate-limiting . H e m e als o
regulates globi n biosynthesis ; th e lowe r th e cel l heme level , th e lowe r th e rat e o f
globin synthesis . A L A - s y n t h a s e i s stimulate d b y steroid s resultin g fro m th e
reduction o f 5/3-dehydr o steroids , suc h a s testosterone . Thi s enzym e appear s i n
h u m a n being s a t puberty .
