Enzymatic decarboxylation of L-threo-3,4-dihydroxyphenylserine in rat heart.
Decarboxylation of L-threo-3,4-dihydroxyphenylserine (L-threo-DOPS) by the higher speed supernatant of the rat heart homogenate and the regional distribution of L-threo-DOPS decarboxylase activity were examined. Decarboxylation was demonstrated to occur specifically with L-isomer but not with D-isomer. Addition of pyrogallol was necessary for maximal recovery of norepinephrine. The optimal condition for decarboxylation of L-threo-DOPS by the rat heart enzyme was similar to conditions required with the enzymes from brain and kidney. Under the optimal conditions, Km and Vmax for L-threo-DOPS were 2.1 mM and 6.4 nmoles/mg protein/15 min, respectively. Decarboxylation of L-threo-DOPS  was markedly inhibited by D-threo-DOPS and D-DOPA. The L-aromatic amino acid decarboxylase activity was highest in the right auricle followed by the atrial body, the left auricle, the right ventricle and the left ventricle.
D000818:Animals; D002262:Carboxy-Lyases / Q000378:metabolism*; D003653:Decarboxylation; D004295:Dihydroxyphenylalanine / Q000494:pharmacology; D015103:Droxidopa / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D009206:Myocardium / Q000201:enzymology*; D009638:Norepinephrine / Q000096:biosynthesis; D011732:Pyridoxal Phosphate / Q000378:metabolism; D011748:Pyrogallol / Q000494:pharmacology; D051381:Rats; D012694:Serine / Q000031:analogs & derivatives*; D013696:Temperature; D013997:Time Factors
D011748:Pyrogallol; D012694:Serine; D011732:Pyridoxal Phosphate; D004295:Dihydroxyphenylalanine; D002262:Carboxy-Lyases; D015103:Droxidopa; D009638:Norepinephrine