Reaction Specificity of Native and Nicked 3,4-Dihydroxyphenylalanine Decarboxylase *

摘要: Abstract 3,4-Dihydroxyphenylalanine (Dopa) decarboxylase is a stereospecific pyridoxal 5′-phosphate (PLP)-dependent α-decarboxylase that converts l-aromatic amino acids into their corresponding amines. We now report reaction of the enzyme with d-5-hydroxytryptophan or d-Dopa results in time-dependent inactivation and conversion PLP coenzyme to pyridoxamine PLP-d-amino acid Pictet-Spengler adducts, which have been identified by high performance liquid chromatography. also show specificity Dopa toward aromatic amines depends on experimental conditions. Whereas oxidative deamination occurs under aerobic conditions (Bertoldi, M., Moore, P. S., Maras, B., Dominici, P., Borri Voltattorni, C. (1996) J. Biol. Chem. 271, 23954–23959; Bertoldi, (1998)Biochemistry 37, 6552–6561), half-transamination reactions take place anaerobic Moreover, we examined nicked decarboxylase, obtained selective tryptic cleavage native between Lys334 His335. Although this enzymatic species does not exhibit either activities, it retains large percentage transaminase activity d-aromatic displays slow These transamination occur concomitantly formation cyclic coenzyme-substrate adducts. Together additional data, thus suggest can exist as an equilibrium among “open,” “half-open,” “closed” forms.