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B6db references: 26832171

type Journal Article
authors Kilpatrick K, Pajak A, Hagel JM, Sumarah MW, Lewinsohn E, Facchini PJ, Marsolais F.
title Characterization of aromatic aminotransferases from Ephedra sinica Stapf
journal Amino Acids
sel selected
ui 26832171
year (2016)
volume 48
number 5
pages 1209-20
keywords Aminotransferase; Aromatic amino acids; Ephedra sinensis Stapf Ephedraceae; L-Tyrosine; Pyridoxal 5′-phosphate; Transcriptome analysis
abstract Ephedra sinica Stapf (Ephedraceae) is a broom-like shrub cultivated in arid regions of China, Korea and Japan. This plant accumulates large amounts of the ephedrine alkaloids in its aerial tissues. These analogs of amphetamine mimic the actions of adrenaline and stimulate the sympathetic nervous system. While much is known about their pharmacological properties, the mechanisms by which they are synthesized remain largely unknown. A functional genomics platform was established to investigate their biosynthesis. Candidate enzymes were obtained from an expressed sequence tag collection based on similarity to characterized enzymes with similar functions. Two aromatic aminotransferases, EsAroAT1 and EsAroAT2, were characterized. The results of quantitative reverse transcription-polymerase chain reaction indicated that both genes are expressed in young stem tissue, where ephedrine alkaloids are synthesized, and in mature stem tissue. Nickel affinity-purified recombinant EsAroAT1 exhibited higher catalytic activity and was more homogeneous than EsAroAT2 as determined by size-exclusion chromatography. EsAroAT1 was highly active as a tyrosine aminotransferase with α-ketoglutarate followed by α-ketomethylthiobutyrate and very low activity with phenylpyruvate. In the reverse direction, catalytic efficiency was similar for the formation of all three aromatic amino acids using L-glutamate. Neither enzyme accepted putative intermediates in the ephedrine alkaloid biosynthetic pathway, S-phenylacetylcarbinol or 1-phenylpropane-1,2-dione, as substrates.
last changed 2019/05/13 09:56

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