Biosynthetic enzymes of tetrahydrolimipterin from green sulfur bacterium Chlorobium limicola

Dongmin Kang, Sangjoon Kim, Jeongbin Yim

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13 Scopus citations


Based on the structure of limipterin (Cha, Pfleiderer, and Yim, Helv. Chim. Acta, 78: 600-614, 1995), the biosynthetic pathway for the newly identified pterin glycoside was investigated. It was demonstrated that tetrahydrolimipterin (H4-limipterin) can be synthesized from GTP by the enzymes GTP cyclohydrolase I, 6-pyruvoyltetrahydropterin (PTP) synthase, sepiapterin reductase and limipterin synthase, present in the extract of Chlorobium limicola. Limipterin synthase (UDP-N-acetylglucosamine:5,6,7,8- tetrahydro-L-biopterin 2'-O-β-N-acetylglucosaminyl transferase) catalyzed the condensation of tetrahydrobiopterin (H4-biopterin) with UDP-N-a- cetylglucosamine in the presence of dithiothreitol and MnCl2. It could also produce D-tepidopterin, [1-O-(D-threo-biopterin-2'-yl)-β-N- acetylglucosamine] when 5,6,7,8-tetrahydro-D-threobiopterin and UDP-N- acetylglucosamine were used as substrates. Substrate analogues such as UTP, UDP and UDP-N-acetylgalactosamine inhibit the enzyme activity. The K(m) values for tetrahydrobiopterin and UDP-N-a-cetylglucosamine were 42.2 μM and 124.3 μM, respectively. Optimum pH and temperature were pH 8.0 and 37°C. The molecular weight of the enzyme was calculated to be 46,300 dalton from a calibrated Superdex 75 and the subunit molecular weight was estimated at 46,000 dalton by SDS-PAGE. These results suggest that limipterin synthase exists as a monomer. Biosynthetic intermediates of H4-limipterin such as H2NTP, 6-PTP, and H4-biopterin were identified in vitro using purified GTP cyclohydrolase I, PTP synthase, sepiapterin reductase, and limipterin synthase. From the HPLC and TLC analyses of the enzymic intermediater, it could be concluded that H4-limipterin comes from GTP by way of H4-biopterin in Chlorobium limicola.

Original languageEnglish
Pages (from-to)69-84
Number of pages16
Issue number2
StatePublished - Jun 1998

Bibliographical note

Funding Information:
This work was supported in part by the Korean Ministry of Health and Welfare, Project No. HMP-96-D-4-1038 to J.Y.


  • Chlorobium limicola
  • GTP cyolohydrolase
  • Green sulfur bacteria
  • Limipterin synthase
  • PTP synthase
  • Sepiapterin reductase
  • Tetrahydrolimipterin


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