Dopa decarboxylase activity of the living human brain.
Monoaminergic neurons use dopa decarboxylase (DDC; aromatic-L-amino-acid carboxy-lyase, EC 4.1.1.28) to form dopamine from L-3,4-dihydroxyphenylalanine (L-dopa). We measured regional dopa decarboxylase activity in brains of six healthy volunteers with 6-[18F]fluoro-L-dopa and positron emission tomography. We calculated the enzyme activity, relative to its Km, with a kinetic model that yielded the relative rate of conversion of 6-[18F]fluoro-L-dopa to [18F]fluorodopamine. Regional values of relative dopa decarboxylase activity ranged from nil in occipital cortex to 1.9 h-1 in caudate nucleus and putamen, in agreement with values obtained in vitro.
Positron Imaging Laboratories, Montreal Neurological Institute, Quebec, Canada.
A
A
Gjedde
J
J
Reith
S
S
Dyve
G
G
Léger
M
M
Guttman
M
M
Diksic
A
A
Evans
H
H
Kuwabara
D001921:Brain / Q000000981:diagnostic imaging / Q000201:enzymology*; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives / Q000378:metabolism; D004296:Dopa Decarboxylase / Q000378:metabolism*; D005462:Fluorine Radioisotopes; D006801:Humans; D007700:Kinetics; D008279:Magnetic Resonance Imaging / Q000379:methods; D008433:Mathematics; D009928:Organ Specificity; D012016:Reference Values; D014055:Tomography, Emission-Computed / Q000379:methods
D005462:Fluorine Radioisotopes; C043437:fluorodopa F 18; D004295:Dihydroxyphenylalanine; D004296:Dopa Decarboxylase