ABSTRACT
BACKGROUND: The phenolic amine synephrine is a vascoconstrictor and bronchiectatic agent and holds promise as an aid to weight management and obesity reduction. Synephrine is structurally similar to the active ingredients of several commercial cold remedies. Some Citrus contain high concentrations of synephrine. An enzyme involved in synephrine biosynthesis, tyrosine decarboxylase (TYDC), is a pyridoxal-5'-phosphate (PLP)-dependent enzyme that decarboxylates tyrosine to yield CO(2) and tyramine. We used PCR to screen, clone and sequence this gene from various synephrine producing and nonproducing Citrus species and varieties to determine if DNA sequence of this gene correlated with synephrine presence. RESULTS: PCR amplification and comparison of DNA sequence indicates DNA sequence differences that may cause production of truncated proteins to be produced in some nonsynephrine producing Citrus. CONCLUSION: Synephrine production may be genetically determined in part by the gene for TYDC.
Subject(s)
Citrus/enzymology , Citrus/genetics , Polymerase Chain Reaction/methods , Synephrine/biosynthesis , Tyrosine Decarboxylase/genetics , Amino Acid Sequence , Base Sequence , Biosynthetic Pathways , Cloning, Molecular , Expressed Sequence Tags , Gene Expression Regulation, Enzymologic , Gene Expression Regulation, Plant , Genes, Plant/genetics , Molecular Sequence Data , Sequence Alignment , Sequence Analysis, DNA , Sequence Homology, Amino Acid , Synephrine/chemistry , Tyrosine Decarboxylase/chemistry , Tyrosine Decarboxylase/metabolismABSTRACT
The metabolism of (+/-)-o-octopamine and (+/-)-o-synephrine by rats was studied quantitatively by a gas chromatography-mass spectrometry-selected ion monitoring (g.c.-m.s.-s.i.m.) method using deuterated internal standards. When o-octopamine was injected intraperitoneally into rats four metabolites were excreted in the urine: (i) unconjugated o-hydroxymandelic acid (OHMA) (16%), (ii) unconjugated o-hydroxyphenylglycol (OHPG) (4.5%), (iii) an acid-hydrolysable conjugate of OHPG (28%) and (iv) unconjugated o-octopamine (10%). When o-synephrine benzoate was similarly administered six metabolites were excreted in urine: (i) unconjugated OHMA (13.5%), (ii) unconjugated OHPG (3.3%), (iii) an acid-hydrolysable conjugate of OHPG (15.6%), (iv) unconjugated o-synephrine (10%), (v) an acid-hydrolysable conjugate of o-synephrine (8.5%) and (vi) unconjugated o-octopamine (0.3%). Adult rats normally excreted OHMA (1.0 micrograms day-1) but OHPG, o-octopamine and o-synephrine could not be detected in urine. After the administration of a monoamine oxidase inhibitor, unconjugated o-octopamine (0.3 micrograms day-1) was excreted in urine but OHPG and o-synephrine could not be detected. o-Tyramine given to rats afforded urinary o-octopamine (75 ng day-1) and this was increased 10-fold upon co-administration of a monoamine oxidase inhibitor and o-tyramine.
