Format

Send to

Choose Destination
See comment in PubMed Commons below
FEBS Lett. 2003 Jul 17;547(1-3):56-60.

The first committed step reaction of caffeine biosynthesis: 7-methylxanthosine synthase is closely homologous to caffeine synthases in coffee (Coffea arabica L.).

Author information

  • 1Faculty of Bioresource Sciences, Akita Prefectural University, Akita City, 010-0195, Akita, Japan. koumno@akita-pu.ac.jp <koumno@akita-pu.ac.jp>

Abstract

In coffee and tea plants, caffeine is synthesized from xanthosine via a pathway that has three methylation steps. We identified and characterized the gene encoding the enzyme for the first methylation step of caffeine biosynthesis. The full-length cDNA of coffee tentative caffeine synthase 1, CtCS1, previously isolated by the rapid amplification of cDNA ends was translated with an Escherichia coli expression system and the resultant recombinant protein was purified using Ni-NTA column. The protein renamed CmXRS1 has 7-methylxanthine synthase (xanthosine:S-adenosyl-L-methionine methyltransferase) activity. CmXRS1 was specific for xanthosine and xanthosine 5'-monophosphate (XMP) could not be used as a substrate. The K(m) value for xanthosine was 73.7 microM. CmXRS1 is homologous to coffee genes encoding enzymes for the second and third methylation steps of caffeine biosynthesis.

PMID:
12860386
[PubMed - indexed for MEDLINE]
Free full text
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for Wiley
    Loading ...
    Support Center